I know a guy from a prominent Chassidish family. Today he is an older Chassidishe Rav in Meah She'arim who gives Shiurim in a yeshiva of Balai Teshuva... He once told me that when he was young and freshly married, he had a business. One day, something went really wrong in his business and he lost almost everything. He became depressed and lay in bed for days. He was unable to daven and even to put on teffilin. And this really bothered him. He couldn't understand. He was asking himself:

Do I believe in Hashem or not?
Do I believe in the Torah?
What are my true motives?
What is my deal?
Am I really doing this all for myself??

When he felt a bit better, he started going to various Gedolim and Rebbes and asking them these questions. "How can it be I was always religious, raised religious, it's in my blood, yet I was able to just lay in a depression and do nothing for days?? Do I believe or not?" And none of them could answer him satisfactorily...

Until he met the son of the ba'al Hasulam, Rav Baruch Shalom Ashlag Za"l... and when he asked him these questions he received answers to them all. Everything became clear. It turned out that he really didn't believe. He had thought he believed, but his belief was not much different than the Arabs who are raised to believe in 72 virgins. He stayed by this Rav for years and through him he learned what real Emunah is, and how one can achieve it. It is only by completely letting go of the self that the true light of Emunah can flow into a person....

See this post from Duvid Chaim for more on this idea.

(See here for some deep Hashkafa ideas from the Ba'al Hasulam about why Hashem gave us the Torah and Mitzvos. After all, what does Hashem gain by making us do them? Couldn't He just give us the good He wants to give us without making it so hard?)