Should i accept the relationship is over?

Hi there,
I don’t know if I should accept that my boyfriend of 4 years and I should go our separate ways or not… To be completely honest and probabky sound slightly pathetic I don’t want to but after a strange incident with another girl (they briefly kissed) I feel it is almost compulsory? The circumstances in which it happened would kind of predict its occurence- big wild drinking session abroad. But pretty much the same thing happened 2 years ago (another kiss with another girl) so it’s a bit odd. He did tell me without very much hesitance about the event both times and is sorry. Now he feels i deserve more and says he’s not good enough etc but we are so in love and get on so well and i feel meant to be. I would be completely devestated if we were to break up. I mean utterly and totally devestated. Should i cut my ties and lose someone i love so much or hope that because we are young these kind of mistakes are bound to happen? Especially when alcohol is involved.