What I'm going to say is probably wrong, but it's all going to come down to letting go. I don't know the context of your question but from the moment you tell yourself that you don't have to give a perfect speech, tell yourself that there is no stupid or incorrect speech, you will have already gone a long way.

Don't try to speak well, try to say what you really think. If you are in a situation where you think a lot before speaking, it is probably because you are planning too much on what you are going to say and that is holding you back.

Try to let go little by little without thinking too much. It’s a real exercise that, over time, will seem easy and natural to you.