Later, when the Germans occupied Poland at the beginning of World War Two, Rev Velvel fled from Warsaw to Vilna. The roads were filled with German troops, and Nazis were everywhere. The danger was awesome. Yet, Reb Velvel traveled along undaunted, for he never stopped reviewing the pledge of the Nefesh HaChayim. "If you always think of Hashem. He will always think of you and protect you from all harm."
Just once, Reb Velvel was distracted and his mind wondered onto another thought. Immediately, as if from nowhere an armed Nazi approached him threateningly. In a flash, Reb Velvel collected his thoughts and focused on the Nefesh HaChayim and the Nazi moved on.(Rabbotainu p 170)
ובאמת הוא ענין גדול וסגולה נפלאה, להסר ולבטל מעליו כל דינין ורצונות אחרים, שלא יוכלו לשלוט בו ולא יעשו שום רושם כלל. כשהאדם קובע בלבו לאמר: הלא ה' הוא האלוקים האמתי, ואין עוד מלבדו יתברך שום כח בעולם וכל העולמות כלל, והכל מלא רק אחדותו הפשוט יתברך שמו, ומבטל בלבו בטול גמור, ואינו משגיח כלל על שום כח ורצון בעולם, ומשעבד ומדבק טוהר מחשבתו רק לאדון יחיד ברוך הוא, כן יספיק הוא יתברך בידו.
קא אמרינן (דברים ד, לה) אין עוד מלבדו אמר רבי חנינא ואפילו כשפים ההיא איתתא דהות קא מהדרא למישקל עפרא מתותיה כרעיה דרבי חנינא אמר לה שקולי לא מסתייעא מילתיך אין עוד מלבדו כתיב והאמר ר' יוחנן למה נקרא שמן כשפים שמכחישין פמליא של מעלה שאני ר' חנינא דנפישא זכותיה: ואמר ר' חנינא אין אדם נוקף אצבעו מלמטה אלא א"כ מכריזין עליו מלמעלה שנאמר (תהלים לז, כג) מה' מצעדי גבר כוננו (משלי כ, כד) ואדם מה יבין דרכו.
The Gemara relates other statements of Rabbi Ḥanina: With regard to the verse: “There is none else beside Him” (Deuteronomy 4:35), Rabbi Ḥanina says: And even sorcery is ineffective against the will of God. The Gemara relates: There was a certain woman who would try to take dust from beneath the feet of Rabbi Ḥanina in order to perform sorcery on him and harm him. Rabbi Ḥanina said to her: Take the dust, but the matter will be ineffective for you, as it is written: “There is none other beside Him.” The Gemara asks: But doesn’t Rabbi Yoḥanan say: Why is sorcery called keshafim? It is an acronym for makhḥishin pamalya shel mala, meaning: That they diminish the heavenly entourage [pamalya], indicating that they function contrary to the will of God. The Gemara answers: Rabbi Ḥanina is different, as, because his merit is great, sorcery has no effect on him. And Rabbi Ḥanina says: A person injures his finger below, on earth, only if they declare about him on high that he should be injured, as it is stated: It is of the Lord that a man’s goings are established; and a man, what does he understand of his way (see Psalms 37:23 and Proverbs 20:24).
Rabbi Yosef Leib Bloch of Telshe (Shiurei Daat II:44) explains that natural forces which threaten mankind can be compared to a vicious dog with a long leash tied to its neck. When the animal pounces, the only way an intended victim can save himself is by calling to the dog's master, to restraint the beast. If the victim fails to recognize the presence of the master then he is truly in grave danger. Similarly when man fails to perceive the "leash" upon the forces of nature, he indeed places himself at their mercy.(Igeret HaRamban, R' Feuer, Chaf Tet, Artscroll)