When you're with other believers, whose interests are you concerned with the most: yours or those in your Christian family? Paul speaks of being selfless amongst other believers. Focus on caring for the appropriate pleasures that others would appreciate more than seeking your own desires. And then Paul added that even Christ didn't live to please Himself.
This is played out in our daily lives in our prayer life (putting other's requests before our own); in our family life (seeking to please your mate and your other family members more than getting your own way); in your church family (again, seeking to build up your brothers and sisters in Christ and help them to do what pleases the Lord); and in your work/school/recreational life (seeking the welfare of others and living so they can see Jesus in you by your kind concern for them).
Selfish behavior amongst Christians should be a oxymoron. If you're a Christian you're not supposed to be self-centered. If you're self-centered, then others have a right to question your Christian commitment. Believers seek to live like Christ, as our Daily Verse points out: "For even Christ did not please Himself."