The prophet -s.a.a.w.- said "Deeds are by their intentions, and to every person whatever it is that he intended. So if someone makes Hijra (immigration) for God and his prophet, then his Hijra is for God and his prophet, and whomever makes Hijra for a worldly target or a woman to marry, then his Hijra is for that which he made it for."
The prophet -s.a.a.w.- also told of the three great people; A scholar, A mujahid warrior who died a martyr, and a rich philanthropist, who all went to Hellfire. When they were asked what they did in their lives and they counted the great actions, they were told they are LYING, and they did those things to BE CALLED great scholar, brave warrior, and generous charitable benefactor.
It is the established belief of Sunnah that good deeds has to be for Allah's sake, in order for us to receive a reward for it. Selfish reasons or hidden agendas nullify the reward, and worst of all is Riyaa', lower shirk, which is doing deeds to show others you are good.
Feeling good about a deed though is not a nullifier of good deeds for there is no evidence of that, and it goes naturally with every person whoever disciplined his soul and self to love and rejoice with goodness. Also evidence shows that having the intention of helping others or benefiting mankind or any of God's creatures or Islam, is also worthy of God's reward, like the man who felt sorry for the dog and gave it water when he saw it thirsty and therefore the prophet said his sins were forgiven.
However we must learn to ALWAYS have God in our hearts when we think of doing good deeds, or the intention of helping and benefiting others and Islam.
