It's hard. Sometimes, it's really REALLY hard.
You have a decision to make. It requires some hard honest truths. Are you really ready to let go? Only you can answer that question. We can give you advice, share our experiences with you, but when it comes right down to it...only you can decide if you have really had enough.
When you have had enough, it won't matter what he says or what he promises. You will just be done. Being done is a very freeing feeling. You will know in your heart and soul that you won't be swayed, no matter what.
When you reach that point, you will know. It will be final. You will do whatever it takes to save yourself. Much like the addict knows when he is done. He will be willing to do whatever is necessary to save himself.
You should strive to take care of yourself. He will survive because that's what addicts do.