Why Must One Rush to Repent for Bad Deeds?

Rabbenu Yona says in the beginning of Shaarei Teshuva, that sin is a stain on the neshama . While we are alive it’s easy to remove the stain: You do teshuva and the stain is removed. If a person who does not teshuva, he dies with a stain and goes to Gehinnom. They put detergents on him to get the stain out. And the detergents hurt... oooohhh do they hurt! They burn! So the neshama is somewhat scarred from its experience in Gehinom. Therefore we shouldn’t wait until Gehinom in order to get rid of the stain. Do teshuva while you’re still alive. — Adam's Ordeal (#28)