Complete emuna in Hashem means that we believe - without any doubt - that He directs and observes each of us individually with exacting precision, and He sees what we don’t see.
In short, complete emuna gives us the peace of mind that Hashem is doing everything for our ultimate good, regardless of the fact that this is not revealed to us at the time.
Therefore, a person should tell himself:
Once we believe that they're for the best, and we thank Hashem for them, they truly become the most beneficial assets in our lives.
Just thank Hashem and see for yourself.
First Emuna, Then Understanding