I feel like this advice could also somewhat apply to your manner of speaking. I'm a pretty fast speaker, and I've noticed that when I try my best to go slower, I understand what I'm trying to say better, I figure out gaps in logic and errors in the sentence while speaking, instead of after, and I get the message across better. And when I'm giving an impromptu speech of some sort, if I slow down and think about every sentence I say, the sentences stitch themselves together in a better-flowing way, and I enjoy speaking because it sounds better.
I, too, speak ridiculously fast. People laugh at me and some (a lot of) people have problems understanding me. As much as I try, as soon as I am not paying attention I speak at the same pace again. Did you manage to slow down your speech consistently?
