Samah siddhav asiddhau ca. If you are working for Krishna, it is Krishna’s decision whether you are successful or not successful. The word here is asiddhau. This means don’t think that because you are Krishna conscious, you will always be successful, for it really doesn’t matter. If you are unsuccessful, then be assured that this is Krishna’s arrangement. To know and accept this is to be Krishna conscious … So never be depressed because you are unsuccessful. A devotee is never depressed in this horrible condition of life. Tat te ’nukampam su-samiksamano bhunjana.

Srila Prabhupada Lecture – BG 4.22 – Bombay 74