When we hear that HaShem created the world to bestow good upon us, we can know with certainty that the extent of this good is beyond our comprehension, just as HaShem Himself is beyond our comprehension.
Which means the following: Imagine the most enjoyable thing that could possibly happen to you. Don't limit yourself, really push your imagination to the limits on this one. Think. You have an idea in your head? Good. HaShem's good which He is bestowing and will continue to bestow upon us is infinitely greater than the enjoyable idea you have in your head right now.
The greatest outcome we could possibly imagine isn't even close to what HaShem has in store for us.
That's a really exciting thought when you manage to internalize it.
Of course this can't be the root of Emunah and Bitachon, why? The Vilna Gaon teaches in his commentary on Mishlei (3:6 I believe) that Emunah and Bitachon are not complete as long as you have any rational crutch upon which to support them.
This understanding we just achieved is a rational crutch.
We have to know and expect that HaShem will provide for all our needs, with utmost certainty, and without any heshbonoth, any rationalization.