"Old Self" in the Bible: Romans 6:5-7
Letting our old self die is hard to do. We've gotten used to our sinful ways, yet we know that now that Christ has come and been resurrected we need to put that old self to death, to let it be crucified as Christ was. It only then that we will be free from sin.
http://biblegateway.com/passage/?search=Rom.6.5-Rom.6.7&version=NIV