Many will say they are really good speakers and yet, they feel they are very poor writers. Many extremely good writers exhibit very poor speaking skills. For instance, if you watch C-SPAN book review you will see some of the best writers you could ever imagine are not very good speakers all. And yet sometimes you see a very good storytellers on the book review channel, which has written a very good book.
Before I started doing a lot of writing, I was a very good speaker and having dabbled in politics I've given quite a few speeches in my life to audiences of all sizes up to about 1000 people. And I've done many TV interviews, one of which was seen by 60 million people. I always considered myself a very good speaker for some reason, perhaps all the practice I got in my own business, but never really considered myself a very good writer.
One day I realized that writing and speaking are very similar and if you write as if you are talking to a group of people or an audience you're writing takes on a whole different shape and meaning. And believe it or not it is even also better received. For some reason people like to be talked to or converse with the writer. If you write as if you're having a conversation with them they are more apt to read what you're writing.
This is why writing and speaking go hand-in-hand, even if you often observe people that are good at one or the other, but not both. A very good writer can become a very good speaker or a very good speaker can become a very good writer. This is because the skills involved are methods of communication and our language. I hope you will understand this and think about it on a philosophical basis because I guarantee you it will either improve your writing or your speaking, or both at the same time.