Humbly regard the other as more important than yourself and look out for the interest of the other. Is Christianity all about self-loathing? Is this what Paul is advocating for? While it would appear so, this is not the case. Love of the self is central to the message of Christ and the gospels: ‘Love your neighbor as you love yourself…’ (cf. Mark 12:30-31). The self is central to the message of the gospels (message of love) because it is to the self that the Lord is revealed, and it is in the self that the first seed of love is planted. When Paul talks about regarding others as more important, therefore, he is not advocating a loathing of the self. Rather, Paul is calling the people to a more practical way of living the gospel teaching. 
Paul predicates his call to a practical way of living the Gospel teaching on humility, the virtue which must be embodied by a follower of Christ. Paul knows that regarding the others before the self is unnatural. It is something that goes against human nature (survival instinct) and as such is not considered a “virtue” in some cultures. However, if tempered by humility, it becomes ‘doable.’ Moreover, for followers of Christ, it becomes a possibility because of the unity (oneness) they have in Christ. Because of the one Christ, the one baptism, and participation in the one Spirit, followers of Christ have ceased from being individual members and have become one body and one mind. In other words, every member of the community will be looking out for the interests of the other, and each will be regarded by the other as more important than the self. In such a scenario, everybody will be important, and everybody will come first.