I am often impulsive?

i just thought it was growing up but i am older now and i still do things i have know thought or control over i don't regret a lot of them but some i do. example of how i can be i had not had a lot to drink but a friend of mine was annoying me slightly and i threw my drink over him and to make it up to him bought him another one. i have punched people randomly when they do annoying little things it's not like i am angry just impulsive and other actions not all ways when people annoy me like having in a public place or some thing. what causes me to be impulsive