Should I end this relationship?

A while ago my boyfriend broke a very important promise to me and it made me extremely upset, so much so that I think of it every day. I have found that I can't seem to love him anywhere near as much as I did before it happened and I don't think it's healthy for either me or him. Is there any chance I might be able to overcome this or do you think that it's a permanent scar on our relationship which isn't going to heal? Do I need to find another relationship and start fresh?