Thoughts occur at rattling speed. 

We can’t speak clearly.
We fumble, stammer or ramble. 

Is this what happens when you start presenting your point of view? 

Could be an interview.
An office presentation.
A family gathering. 

Here is what helps to speak effectively:

Because writing is slow.
We cannot write as fast as we think.
So when we write, we find a way to pace our thoughts.
We find a way to get into a rhythm. 

The best way to express your thoughts clearly, is to write your thoughts before you speak.