Because of our fallen human nature, we are addicted to self. By nature, we constantly think about ourselves and are so far out of touch with reality that we automatically think of ourselves as the center of the universe.
To free us from our addiction to self, God became a human being. He was not addicted to His Self. He even emptied Himself (Phil 2:7) and died on the cross for us. In this way, He broke the spell of self over the human race.
When we are baptized into Jesus and into His death and resurrection (see Rm 6:3), we receive a new nature, free from the addiction to self. When we sin and fail to live our Baptisms, we "fall off the wagon" and return to our self-aholism. When we repent and renew our Baptisms, we are free again from our addiction to self.
In Lent, we prepare to renew our baptismal promises at Easter Vigil or Easter Sunday Mass. Thus, Lent is a time of denying ourselves and even dying to ourselves (see Jn 12:24). Then we can love ourselves and not be dominated by our addiction.