Many religions view the afterlife as eternal, totally spiritual, one in which the individual somehow sheds all vestiges of the present physical existence, and finally succeeds in liberating oneself from imperfection, if not from one's own self and individual identity. The individual is reduced from being a person to a force, spending all eternity with other powers in the universe.
The afterlife promised by Our Lord, Jesus Christ, is something totally different. The Lord took on flesh so as to offer himself to the Father in payment for the sins of the flesh, and, in exchange, offered to us an eternity with God. We who are baptized into Christ's death and resurrection, therefore, do not strive to lose ourselves, or annihilate our identities. Rather, it is our entire selves, body and soul, which, through Christ, will be reunited after death, not in a timeless, impersonal perfection, but by sharing the very life of the Divine Persons of the Trinity.
St. Augustine once wrote that "God became man so that Mankind could become God." In other words, we were created by God in His image, recreated by His Son who revived us from our sins by becoming like us, dying on the Cross and rising on the third day in the flesh and, at the end of time, will be drawn from the grave by the Holy Spirit so as to live with God forever.
No reincarnation is necessary, since we are already remade in Christ. No self-annihilation, since we are precious in the eyes of God through Christ. No losing of oneself into the powers of the universe, since we will find perfection, body and soul, sharing God's life as His beloved.
That is eternal life -- God's love poured out for us in the flesh, so that we can be with God, in the flesh, loving Him and He loving us, His image, forever.