When i split it usually tends to not last very long and so i can do a lot of damage in a short time period and feel instant regret after . Ive come up with a solution for when im feeling like this and im not face to face with the person but im over message.

Basically stop messaging them, take a deep breath, pretend your notes app is a text message. Get it all out. Everything. Sob for a good twnety minutes. Put your phone down for an hours and watch love actually (or your go to comfort show) and then feel much better and a lot less regretful. 

I know its simple and people probably already do this but im dumb and this took me forever to work out. So for my fellow dumb people i hope this helps. It stopped me from permanently destroying my relationships with my FP today so if this helps just one person ill be happy.