How can i stop getting angry quikly?

ok well i get angry pretty easily and i think that's from always being belted as a child for simple child mistakes but if not please some one help me find out why i might have anger problems ... iv been going out with my gf for almost a year and some times she does lil things that piss me off and some times i keep it in then blow up later on and some times i just tell her to eff off but i hate swearing in Generall especially at her and its been happening for some time now and shes really tired of it and honestly so am i like yesterday we were muking around and i got in my car and locked her out looked like she laughed but she didnt and she hit my window and sounded like if she hit it harder it would have cracked and she noes i value my car its nothing special but iv put in like almost 20 hours of labour into it and coz she hit the window hard it really got me angry and i called her a itch and told her to eff off and we went in side and she didnt say sorry so i grabbed her stuff and gave it to her and locked her out of my room then i started to calm down and i saw she started to leave so i went to her car and we spoke a lil bit and she was crying and didnt want to see me and went home and i started to think how stupid a window is easy to fix but a relationship is not and she needs space to think and i was wondering if anyone had good tips on how i can actually think at the moment of that im really angry instead of blowing up at someone? please any advice would be great??