If someone you loved cheated on you, could you forgive them or would there be no path of redemption?

Cheaters have always been the destruction of a relationship with me. Even my 15-year marriage ended because the ex was cheating on me for at least 9 or 10 of those years. We actually get along better as friends now then we ever did when we was married but there could never be another me and her. The pain went way too deep. After all of this I have come to the assumption that people are right when they say... "Once a cheater, always a cheater". I wish I could see it differently but I just can't.