Rabbeinu Yona teaches that we have to see Hashem in everything. We have to ask Him for success in all that we do as we go through our day. This is Mindfulness the Jewish way. Flexing our bitachon muscle when things are going well will help us through the difficult times.
Having bitachon also means that we believe that if Hashem gave us certain mitzvot to do, then we can not lose by doing them! We can rely on Hashem's promises. For example, keeping the Shabbat and eating kosher, giving a tenth to tzedaka, or observing the laws of shmitta will not deplete your earnings. This seems irrational, illogical and counterintuitive but the Master of Bitachon believes that Hashem keeps His promises.