go to your favourite site.
get some stuff you like.
control yourself

Don't care about anything. Spongebob's your best friend. Homer Simpson too.

Just remember that people who insult you on the internet, probably are insecrue in their real life and takes out their anger on random people online.

It's a surprisingly hard habit to get into it and sounds like stupid advice. But you just gotta think about what you're doing and if it it's actually okay. If you're angry. You need to figure out how to become aware you're angry and your actions are simply being done out of anger. Then put a stop to it. It's not an easy task, but it's worthwhile for life in general. But the Steam forums aren't worth such. But life is, so I'd say it's still worthwhile if you think it could be an issue outside of Steam.

Just say no to yourself until you get annoyed and stop.