There is a difference between Emunah (Belief in G – d) and Bitachon (Trust in G – d). Someone may believe that G – d is the Creator of everything existing but this doesn’t mean that he, at the same time, has total trust in G – d (Bitachon).
According to Talmud Kiddushin 82, Bitachon means to be an outstanding pious Jew who is on a high level of Bitachon. Meaning that, whatever happens, G – d will help him. No matter what. Others who are not on such a high level start complaining, as soon as a difficult situation comes up.
Speaking about myself: I am not an extraordinary pious Jew on whatever highest level but I do have a certain level of Bitachon. Even if I have my doubts whether I am getting out of a difficult situation or a problem seems to be without any solution, I still keep up some Bitachon. Also because it helps and provides hope for better times to come.
At the same time we may find ourselves so caught up in our struggles that we forget about G – d and only think about a solution. A solution we provide and not G – d.
I find it very difficult to define Bitachon because only trust in G – d may be not sufficient. Only sitting and thinking that G – d will pop up with a solution is wrong, as He also wants us to take action. As soon as we try solving a problem, He will help us.
It is strange but when we go through difficult times which seem to be so hopeless, something always comes up and, in the end, there is a solution for almost everything.