Philippians 2
Paul calls us (though literally the Philippians, but it nevertheless applies to us too) to act in humility when interacting with others. While we should consider our own interests as well, we should not let our desire to fulfill our interests overcome the desire to fulfill the interests of others—obviously assuming that the interests of others are Biblically acceptable. Having started off with unity, fellowship, being like-minded, et cetera, he follows with an example of Christ, how Christ was with God.
He tells of the equality Christ has with God, whom, seeking to fulfill God's will, chose not to remain in the equality that he had with God but went and separated from that equality, humbling himself from a state of equality with God into a human state, subjecting himself even to death. Hence implying how we should treat each other, that though we may be united and equal in Christ, we should seek to humble ourselves for the sake of others.