My poor therapist has a hearing impairment and has to try to partially read my lips. I have no idea how he knows what I am saying when it gets bad.

Looking back I had this as a child. My family made fun of me all the time for it, as did friends in college and grad school. I learned to control it when I worked with hearing impaired people through most of my career. Some still had trouble but I did have the ability to consciously slow down if I worked at it.