Onesimus, a slave, became a Christian in prison. This made him a son of God and a spiritual child of Paul, who led him to Christ (Phlm 10). In Greek, "Onesimus" means useful. Contrary to his name, Onesimus had been useless, but he became useful when he became a Christian (Phlm 11). Paul found Onesimus so useful that he considered him to be his very heart (Phlm 12). When Onesimus gave his life to Jesus, he became "more than a slave," he became "a beloved brother" of Jesus, of all Christians, and even of his slave-owner, Philemon (Phlm 16).
When someone becomes a Christian, he enters God's family, has a share in the divine nature of the Trinity (2 Pt 1:4), and becomes a member of the body of Christ. Only in Christ is there salvation (Acts 4:12), freedom (Jn 8:36), and eternal life (1 Jn 5:12). In Christ, we are more than conquerors (Rm 8:37). Consequently, a person's life is in some way wasted and useless until he becomes a Christian (1 Pt 4:2). However, in Christ "there is no condemnation" (Rm 8:1).
Therefore, in thanksgiving to the Lord, live for Him alone and tell others the good news of life in Jesus Christ.