The Ribbono Shel Olam gives a person what that person needs to succeed, and success means being able to attain Olam Haba. It might be riches and it might be poverty.
The Chazon Ish says that bitachon doesn’t mean that people should have faith that they will get whatever they hope for; rather, they should have faith that they will get that which is best for them.
A person can have complete faith that Hashem will send him riches, and never get it, because that’s not what bitachon means.
Believe and trust and be sure that Hashem will send you that which is best for you to reach the ultimate goal, and have ultimate success, whether or not you understand it.
At the end, you will.
~ R’ Zev Leff