We stop being slaves to sin and become slaves to Christ. The first gift that comes from God is eternal life. In the Gospels eternal life is not something that happens in the future, it is something that happens as soon as someone believes in Christ. Each Christian receives eternal life when faith takes hold of his or her life. But no matter when it happens, every Christian has eternal life from the moment it happens.
Eternal life makes a difference in our lives even before death.
It radically changes our perspective about what happens in the here and now. Eternal life allows the Christian to turn the temptation of sin into a blessing. Pride makes it all the more humble. Laziness makes it all the more industrious. Greed makes it all the more generous.