Being a dick

I make major mistakes in my life (not very often) but when I do they are enormous. I have learnt from every single one but I am 30 years old now and need to stop being a dick and be the bigger person.
Overall I know myself I am a good person and can admit when I've messed up but recently I've bumped into my boyfriends ex. She had a full blown affair for years and she treated him badly and he left her.
I couldn't hold my tongue and followed her into toilets (was drunk in a bar) where I was calm at first but then ended up calling her a slag. I had never officially met her before and I lowered myself to the vermin that she is.
They have two sons who she told (obviously to make herself look the victim and me look awful). I apologised to them and told them I shouldn't have said anything to their mum and I shouldn't have got involved.
I always feel like I mess everything up. I was doing so well and they really liked me and now I feel the damage is done and they will forever hold it against me. I have awful feeling in pit of my stomach and wish I had a time machine to go back and make sure it never happened but it's done now.

Help