The Gemara (Megillah 16.) states that when Haman came to Mordechai (to lead him through the streets of Shushan, as Mordechai rode on Achashveirosh's horse), he found Mordechai teaching the laws of kemitzah to his students. Kemitzah is to bring a handful of a meal-offering (made of just flour and oil) on the mizbeiach. Haman thought that small deeds are unimportant; only great deeds have value. This was demonstrated by the enormous gift of ten thousand kikar silver coins he offered Achashveirosh. In his eyes, only tremendous and impressive matters have value. Mordechai, on the other hand, taught his students that even a small handful (a kometz) of a minchah is a korban in Hashem's eyes. Every small deed is very precious in Hashem's eyes. In the end, Haman admitted that Mordechai was correct and said, "Your handful of flour pushed away my ten thousand kikars of silver."
One of the benefits of the "small deeds" is that one good deed leads to another, as Chazal say מצוה גוררת מצוה.
Chazal (Shabbos 105:) say, "This is the way of the yetzer hara: Today he tells you to do this [aveirah], tomorrow he tells you to do that [aveirah], until he tells you to worship avodah zarah – and he worships it!" The yetzer hara is happy with minor sins because he cleverly knows that one deed leads to the next. We should learn from our enemy and consider every good deed significant. It is great in Hashem's eyes, and furthermore, one small deed will lead to another good deed, and gradually, we will grow in avodas Hashem.
