I don't believe in karma, because I believe in God's mercy and grace. We are bound to make mistakes and act out. God is a forgiving God, and not one that will cut you down over every mistake given. I do believe that you are rewarded for the good you do though. Whether it be rewarded here or in heaven, God doesn't overlook the good we do.

"Give, and it will be given to you. A good measure, pressed down, and shaken together and running over, will be poured into your lap. For with the measure you use, it will be measured to you." Luke 6:38