Rashi (Bereishis 11:28) writes, "Terach was responsible for the death of his son Haran. Terach complained to Nimrod about his son Avraham who broke his idols and threw the pieces into a furnace. Haran was present, and he thought, 'If Avram wins, I am with him. And if Nimrod wins, I am with him.' When Avram was saved, they asked Haran, 'Which side are you on?' He replied that he was with Avram. So they threw him into the furnace, and he perished."
The Sfas Emes (טעם ה"ד ז"תרל) says that although Haran wasn't perfect (because he had doubts, and he waited to see what will happen to Avraham), nevertheless, he went into fire al kiddush Hashem, and he deserves a reward for that. His reward is that Dovid HaMelech and Moshiach descend from him. (Dovid HaMelech and Moshiach are grandchildren of Haran's son Lot.)
This is because every good deed is rewarded, even when it isn't perfect.
Here's another example: Rashi (21:34) tells us that Lot was captured in the war, Og notified Avraham. Avraham went to the war and saved Lot. Og's good deed (telling Avraham about Lot) didn't come from righteous intentions. Rashi explains that Og wanted Avraham to die in war so he could marry Sarah. Nevertheless, Og did a good deed and was rewarded. As the Midrash (Bereishis Rabba 42:8) states, "Hakadosh Baruch Hu said, 'I swear, you will be rewarded for each step you took [to tell Avraham], and you will live long in this world.'"
Years later, in Moshe Rabbeinu's era, Og was the king of Bashan, and Moshe was afraid to wage war against them. Rashi (Bamidbar 21:34) explains that Moshe feared that Og's merit might protect him.
So we see that every good deed will be rewarded, even the good deeds of reshaim, even when the intentions weren't pure. We can therefore be confident that all our good deeds will be rewarded. This awareness will encourage us to perform as many maasim tovim as we can.
