Self-forgiveness is a derivative of the secular belief that you can't love others until you learn to love yourself. (Which is untrue, by the way.) On a Christian level the idea has been transferred over to essentially say that you can't forgive others until you've forgiven yourself.
The problem is this idea has zero biblical foundation.
The whole idea of self-forgiveness is a concoction of modern, Western thinking that is accustomed to viewing all things through the looking glass of HOW IT AFFECTS ME. Living in the "Selfie Culture" it's normal for us to see ourselves smack dab in the middle of every event of our lives. Wherever we go or whatever we do, there I find "ME" taking up the majority of the camera lens with all else comfortably in the background. It's just the way we've learned to view life and we see nothing strange about it. But it is strange—and damaging too.
As believers, we ought to find ourselves being drawn away from a me-centered existence and more into one where Jesus Christ takes up the majority of the camera lens. His thoughts increasingly become our thoughts, and His truth affects how we believe and think. So when He says we are forgiven, we ought to adjust our thinking accordingly. He is the Master, and His determination of my life trumps my own every time. To say, "But I haven't forgiven myself!" is to elevate my own opinion and feelings above His and only reveals an attitude of self-importance. We need to meditate on Galatians 2:20.
I have been crucified with Christ. It is no longer I who live, but Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me. Galatians 2:20 (ESV)