1 Corinthians 13:4-5 – Love endures long and is patient and kind; love never is envious nor boils over with jealousy, is not boastful or vainglorious, does not display itself haughtily. It is not conceited (arrogant and inflated with pride); it is not rude (unmannerly) and does not act unbecomingly. Love (God's love in us) does not insist on its own rights or its own way, for it is not self-seeking; it is not touchy or fretful or resentful; it takes no account of the evil done to it [it pays no attention to a suffered wrong]. (AMP)
Love’s focus is on improving the life of the beloved rather than on improving only his own life. As he works to accomplish this goal, his own life is in turn blessed. Love is its own reward. It is impossible for love to be selfish or self-seeking. The very nature of love is outward and giving, rather than inward and taking. When a person acts in (what he perceives to be) the best interest of himself alone, he is not acting in love. The lover never puts himself first. The lover always holds the beloved in higher esteem than himself. Once he starts acting in any other way, he ceases to act in love.
On the other hand, neither is love self-deprecating. The lover must love himself in order to truly be able to love the beloved. Otherwise he will act in ways that sabotage the relationship rather than build it up. If the lover does not truly love himself, he will be incapable of fulfilling 1 Corinthians 13:4-8. Sometimes we need to be our own beloved so that we can love those around us better (Matthew 22:39). The lover will involve himself in self-improvement for the purpose of enabling himself to love the beloved better.
Self-sacrifice and self-deprecation are not the same thing. When someone deprecates him/herself for what he/she thinks is the sake of the beloved or the relationship, he/she is really acting in a twisted form of pride which is motivated by the fear of being alone and not being accepted by the beloved. This enables the beloved to continue in sin and gives the beloved unspoken permission to become more depraved. However when the lover sacrifices what he wants for the betterment of the beloved, he acts in a way that brings conviction to the beloved and will not allow the sin to continue. Actions, based out of love, encourage the person to become what God created the beloved to be.