Yes, repentance is a part of salvation. You are repenting of the sins (past, present, and future) that Jesus died for. All sin was covered by Christ at Calvary. That is why we have victory in Christ. I'm trusting in His Substitionary Attonment for my salvation, but I had to realize, by God's grace, that I was a sinner headed for hell and I deserved Hell first. Belief in Jesus alone does not pay for your death penalty. Jesus said repent for the Kingdom of God is at hand. This ment that one day we will all stand before God. The lost will be cast into the lake of fire because the did not repent and accept His Son as payment for their sin. The believers will stand before God and give and account on what they did with God's grace each day. By the way, when I was little I thought I was saved because I believed, but the Holy Spirit didn't move in and start changing my life until I acctually got saved