I cheated on an ex after getting hammered one night. By hammered I mean black-out drunk - which I rarely get. My friend (also v. drunk) told the girl I was too drunk but apparently she just waved it off and I gave him my coat and said see you later (it was mid-winter, below freezing to give you an idea of my mind set).

In this case it made me quickly accept that I wasn't that into my ex. In the morning I spent a couple of minutes feeling sorry for myself but then faced up to that reality. I broke up with her a week later (didn't tell her about the cheating).

My advice mate (assuming you're asking because you've cheated...).

Your relationship is now almost certainly irreparably tainted. You now have two choices: end it or don't tell her and make sure it doesn't happen again. If you can't be sure you won't do it again then end it. And if it's going to effect how you are around her (in a negative way) then end it.

This might split opinion, but in my view you've already done the selfish thing and it's on you to live with it. Telling her is shirking your responsibility for the sake of your conscience; the cliche that you're 'doing the right thing' is complete bollocks. You're asking her to make a decision because of your actions, and she most likely has no idea of what she's signing up for.

She either then has to end it or, if she likes you enough, put herself through a permanently tainted relationship and months of heart-ache, sleepless nights, permanent trust issues, possibly feelings of inferiority and feeling like shit all because you no doubt made a mistake you seriously regret (hence you asking this question). All that time you'll be working towards 'rebuilding trust' and making sure it 'never happens again', which begs the question: what does telling her really achieve in the first place?