It is simply in faith in the finished work of Christ. You cannot and absolutely will not overcome what has you held, until your faith is there. You will not be victorious through any work of your own kind. Oh, you can try.
More than likely you have, and probably have been disappointed by the short term results. It doesn't mean you're not saved! You might just be struggling with your very own self.
After such a sacrifice on His part, Let Jesus have you completely. Your failures and all.
I promise He knows what to do with them.