From Sing, You Righteous by Rabbi Avigdor Miller
The Duties of the Hearts (Bitachon 3) states: “The fourth premise (of bitachon) is that one's attention should be strong and his effort great to fulfill that which his Creator requires.”
Bitachon does not mean to induce oneself to trust without logic. It rather is the awareness that G-d alone controls everything.
Each sin subtracts your awareness that the Creator alone conducts the affairs of the world
Therefore, when one desires something (and who does not desire something?) he must exert himself to gain G-d's favor; if he does not attempt to gain His favor, he thereby demonstrates that he hopes to gain his desires without G-d's help. Thus, whenever one commits a transgression, he thereby falls lower in the degrees of awareness of G-d; for he certainly does not consent to waive his hope to live and to have all his needs, and he intends to attain everything he desires despite his sin against the will of the Creator.
With every additional transgression there is created in him an added impression that even without G-d's wish he can gain his desires. He certainly does not consent to suffer, and he wishes to live in tranquility and prosperity despite his sin; therefore, each sin subtracts from his bitachon and from his awareness that the Creator alone conducts the affairs of the world. The virtuous man develops in the opposite direction for he certainly hopes that G-d will favor him because of his behavior; and therefore his bitachon increases steadily, for it is to his benefit to feel that G-d controls everything.