I brought up Rubashkin twice because this idea of not running to goyim/she ideology for life direction and general well-being etc. he really is enthusiastic about, and he elaborates on his experiences to make it real and down to earth. He explains the Torah principles that support his ability to remain joyous even there, and is currently working on a book on that topic to help people.
As far as how do we know? He heard after he was freed, from one of the inmates, that one guard asked the other, “Who’s the guy that was let out by the President?” The other got thought for a second and said, “You know the guy who was always happy? That one.”
He was told by a well meaning acquaintance after his release, that after the star dust settles, he will most certainly need therapy to adjust to regular life, especially after prison. He didn’t need any therapy because he was never traumatized, because of the constant bitachon work he did.
Obviously he felt pain, but he was never depressed. And he is so intent on helping yidden have this for themselves, no matter the situation, that instead of going back into business, his dream was to learn and mentor yidden in bitachon. Hashem has helped him and he is massively successful BH. He now has six big homes which he used to host people for Shabbatons on the topic, and he also gives weekly shiurim which many people attend from nearby Lakewood, and many people from all over the world are in touch with him as a mentor. He has also spoken worldwide on his experience, and in general is in a different spiritual sphere than most people. His incredible test has only uplifted him through the power of Torah, as can be seen from his before, and after prison life. (Not that his before was bad cvs, he was amazing then too. Just nothing to compare to where he is holding now.)