One must do all he can to try and "repay H'shem the debt of gratitude" and trust H'shem will reward him. "Be not like servants who serve the master on condition of receiving a reward, but be like servants who serve the master not on condition of receiving reward and let the fear of heaven be upon you (Avos)
pg 445
Nefesh Hachaim
Not the Angles not man not even Moshe knew "H'shem's place, only H'shem Himself knows the essence of this hidden and unfathomable idea"
Gate Three, Chapter Six pg 115