One who trusts in H'shem is satisfied with what he has and uses the excess to serve H'shem by helping others. One who does not trust in H'shem never sees what he has as being enough and is always on the chase for more. He will hold his money instead of using it to help others, eventually losing it and having nothing to show for his it.
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Nefesh Hachaim
The goal of the Yetzer Harah when he seeks to destroy a Tzakik is by making the mitzvah's intentions, kedusha, and kavanh more important than the fulfillment of the mitzvah itself. In H'shem's eyes, one who sets out to serve Him should not be bombarded with fear of intentions, and kedusha, he should fulfill the mitzvah at its appointed time with the best intentions he can, knowing he is fulfilling his Torah obligation and it is the most precious thing to H'shem.
Prologue to Gate Four Chapter 4 pg 126