Love yourself as you love your fellow - Judaism's approach to self-love (SOURCES)

(25) If there is worry in a man’s heart let him quash it,
And turn it into joy with a good word.

(9) But take utmost care and watch yourselves scrupulously, so that you do not forget the things that you saw with your own eyes and so that they do not fade from your mind as long as you live. And make them known to your children and to your children’s children:

(17) A kindly man benefits himself;
A cruel man makes trouble for himself.

(1) Since maintaining a healthy and sound body is among the ways of God - for one cannot understand or have any knowledge of the Creator, if he is ill - therefore, he must avoid that which harms the body and accustom himself to that which is healthful and helps the body become stronger.
They are as follows: a person should never eat unless he is hungry, nor drink unless thirsty. He should never put off relieving himself, even for an instant. Rather, whenever he [feels the] need to urinate or move his bowels, he should do so immediately.

Love your fellow as yourself

(1) There are five general forces that need to be tended to so that they should be whole in the life of the collective and the individual. Then, appropriate force will be found in them to keep all damage at a distance to enhance life in the appropriate way. The first is physical and mental health leading to a full and joyous embracing of life. The second are those human forces that are properly developed, the feelings for spiritual delights, beauty, poetry, healthy imagination and included amongst them are those qualities which make for good friendship, founded on the notion that basic decency precedes Torah. The third is the national feeling that needs to be adequately developed in each person according to the character of his nation and its needs, its nature, its position (in the world) such that his heart is alive and his soul senses with a healthy bravery that which is good for his people. He yearns with a living natural love to increase its value and its success. The fourth is developing a religious sensitivity which is a lofty feeling planted in the spirit of a person by the Creator of his soul, in order to imprint in his inner most parts the true relationship between man and his Creator, in the sense of a relation which is appropriate to be between Designer and product. This religious sensitivity embraces all of the foundations of life and ethics in a general and particular sense. The fifth is development of the intellect, knowledge of the universe and Being, wisdoms both speculative, practical and abstract so that one feels a natural necessity to take delight in the glory of abstract wisdom that relates to divinity and all things that accompany its knowledge.

Rather, perhaps the book poses a difficulty because it is written there: Do not introduce anxiety into your heart, as anxiety has killed mighty men (Ben Sira 14:1; 30:29). Didn’t Solomon already say it in the verse: “Anxiety in a man’s heart dejects him [yashḥena]” (Proverbs 12:25)? Rabbi Ami and Rabbi Asi interpret the term homiletically and read it as yesiḥenna. One says that it means: He shall remove it [yesiḥenna] from his mind, and that will ease his anxiety. And one says: He shall tell it [yesiḥenna] to others, and that will ease his anxiety. Both agree with the statement of ben Sira.

The Gemara continues to address the issue of suffering and affliction: Rabbi Yoḥanan’s student, Rabbi Ḥiyya bar Abba, fell ill. Rabbi Yoḥanan entered to visit him, and said to him: Is your suffering dear to you? Do you desire to be ill and afflicted? Rabbi Ḥiyya said to him: I welcome neither this suffering nor its reward, as one who welcomes this suffering with love is rewarded. Rabbi Yoḥanan said to him: Give me your hand. Rabbi Ḥiyya bar Abba gave him his hand, and Rabbi Yoḥanan stood him up and restored him to health. Similarly, Rabbi Yoḥanan fell ill. Rabbi Ḥanina entered to visit him, and said to him: Is your suffering dear to you? Rabbi Yoḥanan said to him: I welcome neither this suffering nor its reward. Rabbi Ḥanina said to him: Give me your hand. He gave him his hand, and Rabbi Ḥanina stood him up and restored him to health. The Gemara asks: Why did Rabbi Yoḥanan wait for Rabbi Ḥanina to restore him to health? If he was able to heal his student, let Rabbi Yoḥanan stand himself up. The Gemara answers, they say: A prisoner cannot generally free himself from prison, but depends on others to release him from his shackles.

(14) He used to say: Beloved is man for he was created in the image [of God]. Especially beloved is he for it was made known to him that he had been created in the image [of God], as it is said: “for in the image of God He made man” (Genesis 9:6). Beloved are Israel in that they were called children to the All-Present. Especially beloved are they for it was made known to them that they are called children of the All-Present, as it is said: “you are children to the Lord your God” (Deuteronomy 14:1). Beloved are Israel in that a precious vessel was given to them. Especially beloved are they for it was made known to them that the desirable instrument, with which the world had been created, was given to them, as it is said: “for I give you good instruction; forsake not my teaching” (Proverbs 4:2).

(13) Rabbi Shimon said: Be careful with the reading of Shema and the prayer, And when you pray, do not make your prayer something automatic, but a plea for compassion before God, for it is said: “for He is gracious and compassionate, slow to anger, abounding in kindness, and renouncing punishment” (Joel 2:13); And be not wicked in your own esteem.

(33) we saw the Nephilim*Nephilim See Gen. 6.4. there—the Anakites are part of the Nephilim—and we looked like grasshoppers to ourselves, and so we must have looked to them.”

(5) How does the court intimidate the witnesses in giving testimony for cases of capital law? They would bring the witnesses in and intimidate them by saying to them: Perhaps what you say in your testimony is based on conjecture, or perhaps it is based on a rumor, perhaps it is testimony based on hearsay, e.g., you heard a witness testify to this in a different court, or perhaps it is based on the statement of a trusted person. Perhaps you do not know that ultimately we examine you with inquiry and interrogation, and if you are lying, your lie will be discovered. The court tells them: You should know that cases of capital law are not like cases of monetary law. In cases of monetary law, a person who testifies falsely, causing money to be given to the wrong party, can give the money to the proper owner and his sin is atoned for. In cases of capital law, if one testifies falsely, the blood of the accused and the blood of his offspring that he did not merit to produce are ascribed to the witness’s testimony until eternity. The proof for this is as we found with Cain, who killed his brother, as it is stated concerning him: “The voice of your brother’s blood [demei] cries out to Me from the ground” (Genesis 4:10). The verse does not state: Your brother’s blood [dam], in the singular, but rather: “Your brother’s blood [demei],” in the plural. This serves to teach that the loss of both his brother’s blood and the blood of his brother’s offspring are ascribed to Cain. The mishna notes: Alternatively, the phrase “your brother’s blood [demei],” written in the plural, teaches that that his blood was not gathered in one place but was splattered on the trees and on the stones. The court tells the witnesses: Therefore, Adam the first man was created alone, to teach you that with regard to anyone who destroys one soul from the Jewish people, i.e., kills one Jew, the verse ascribes him blame as if he destroyed an entire world, as Adam was one person, from whom the population of an entire world came forth. And conversely, anyone who sustains one soul from the Jewish people, the verse ascribes him credit as if he sustained an entire world. The mishna cites another reason Adam the first man was created alone: And this was done due to the importance of maintaining peace among people, so that one person will not say to another: My father, i.e., progenitor, is greater than your father. And it was also so that the heretics who believe in multiple gods will not say: There are many authorities in Heaven, and each created a different person. And this serves to tell of the greatness of the Holy One, Blessed be He, as when a person stamps several coins with one seal, they are all similar to each other. But the supreme King of kings, the Holy One, Blessed be He, stamped all people with the seal of Adam the first man, as all of them are his offspring, and not one of them is similar to another. Therefore, since all humanity descends from one person, each and every person is obligated to say: The world was created for me, as one person can be the source of all humanity, and recognize the significance of his actions. The court says to the witnesses: And perhaps you will say: Why would we want this trouble? Perhaps it would be better not to testify at all. But be aware, as is it not already stated: “And he being a witness, whether he has seen or known, if he does not utter it, then he shall bear his iniquity” (Leviticus 5:1)? It is a transgression not to testify when one can do so. And perhaps you will say: Why would we want to be responsible for the blood of this person? But be aware, as is it not already stated: “When the wicked perish, there is song” (Proverbs 11:10)?