One who does not trust in H'shem does not concern himself with religious issues. He fools himself into believing he will live "forever" and puts all his efforts and interest into this world and very little into his ultimate destination.
pg 455
Nefesh Hachaim
We learn from our sages and Avos that "good deeds" are preferable to wisdom. If one persues mitzvot and good deeds, his roots will be strong even if his wisdom is not great, and his wisdom will be elevated.
Prologue to Gate Four Summation pg 132