Serving Hashem with Love, Joy and a Good heart

(12) And now, O Israel, what does the LORD your God demand of you? Only this: to revere the LORD your God, to walk only in His paths, to love Him, and to serve the LORD your God with all your heart and soul,

(6) Then the LORD your God will open up your heart and the hearts of your offspring to love the LORD your God with all your heart and soul, in order that you may live.

(16) For I command you this day, to love the LORD your God, to walk in His ways, and to keep His commandments, His laws, and His rules, that you may thrive and increase, and that the LORD your God may bless you in the land that you are about to enter and possess.

(5) But be very careful to fulfill the Instruction and the Teaching that Moses the servant of the LORD enjoined upon you, to love the LORD your God and to walk in all His ways, and to keep His commandments and hold fast to Him, and to serve Him with all your heart and soul.”

Moses was sanctified by the cloud and received the Torah at Sinai, as it is stated, And the glory of the Lord abode upon mount Sinai, and the cloud covered him six days. [It covered Moses] in order to cleanse him, and this occurred after [the proclamation of] the Ten Commandments. So expounded R. Jose the Galilean. R. Aḳiba said: The verse and the cloud covered him six days refers to [the mountain and not to] Moses. The continuation of the verse, And the seventh day He called unto Moses out of the midst of the cloud, is to single Moses out for special honour.
R. Nathan said: Why was it that Moses remained on the mountain six whole days without the Word descending upon him? It was that he might be purged of all food and drink which were in his bowels, until such time as he would become holy and be like the ministering angels. R. Mathia b. Ḥeresh said to him, ‘Master, surely the only purpose was to impress him so that he should receive the words of the Torah with awe and fear, with dread and trembling, as it is stated, Serve the Lord with fear and rejoice with trembling.
It is related that R. Josiah and R. Mathia b. Ḥeresh happened to be sitting engaged in the study of the Torah, when R. Josiah departed to pursue some secular affairs. R. Mathia b. Ḥeresh said to him, ‘Master, why do you forsake the words of the living God and immerse yourself in secular affairs? And though you are my teacher and I your pupil, [I venture to say that] it is not right to forsake the words of the living God and immerse oneself in secular affairs’. It was said of them that while they were engaged together in the study of the Torah they were like foes one towards the other, but when they departed they were like lifelong friends.