The only thing separating me and a relationship.?

Maturity. I need to change. Man I cannot stress this enough. I WANT TO CHANGE!! NOT FOR THEM, FOR MYSELF!!! Ok. Thats outta my system. Well. I want to act more mature. I am a funny guy (I guess, people say I am) but sometimes I just act too crazy. I talk WAY to much. I yell things in cl, people look at me funny. You get the point. My question is How do I shut the hell up, and calm the f*ck down? Lol. Excuse my computer lingo. Also how do you change your personality in such a way? I want to start thinking before I speak. But how do I go about that? It's like instinct for me to just blurt it out. I hope you were able to understand this. Thanks in advance.