Why do the words find my pen so appealing and my mouth the opposite?

Why can my Writings express my feelings and my speech barely even scratch the surface?

Where can I find a happy medium between my pen and my mouth
Because it's really killing me to have all these thoughts swirling around in my brain, and not being sure about how they'll come out

Sometimes one moves faster than the other
And it's annoying, not funny like undercover brother

So if anyone knows how, please tell me what am I to do?
Because my head is wired more chaotically than the San Diego zoo