“Be careful not to practice your righteousness in front of others to be seen by them. If you do, you will have no reward from your Father in heaven. “So when you give to the needy, do not announce it with trumpets, as the hypocrites do in the synagogues and on the streets, to be honored by others. Truly I tell you, they have received their reward in full. But when you give to the needy, do not let your left hand know what your right hand is doing, so that your giving may be in secret. Then your Father, who sees what is done in secret, will reward you. Matthew 6: 1-4
We do not serve others in order that we might receive a special blessing. God does not operate a karma wheel.
Serve or give in God's name from the compulsion of your heart's desire to help someone else. When you give or serve because you are "supposed to do it", then you working to please others or maybe even yourself instead of desiring to please God.
There is nothing wrong with helping others for any reason ... but there is a difference between doing a good deed and serving in the name of God. It's a fine line... but when you get the heart right - and the service God exepects of us will follow naturally. You won't have to worry about it.