I think everyone on here has had a similar experience and can relate. Try to focus on moving forward and NOT rehashing this in your mind and torturing yourself. What I have found very helpful is diaphragmatic breathing and slowing down. Also, focus on trying to RELAX all the muscles in your body before speaking. I know all this is easier said than done, but practice and keep practicing these techniques (or any others you find helpful). By having a purpose to focus on (getting more fluent)it helps to take your mind off past situations. Please hang in there, you are not alone!!