I am the exact same way as well. When I have to give presentations or conduct trainings at work I can speak really well during practice sessions, but on the big day I get stuck. What tends to help me is 1. When practicing I try to replicate my anxiety of presentation day. Just picturing faces of ppl looking at me and get my heart rate up (to mimic anxiety), that way I get used to that feeling during practice sessions. 2. I memorize the opening few lines so that I can get into the groove for the main content of my presentation. Trying to improvise at the start of the presentation, with the heart racing and speech block is not fun. Once I hit the groove in the presentation, then I'm fine. 3. I barely stutter with family and close friends. It's when I talk to strangers or acquaintances do I get a speech block the most. Networking events for me are the absolute worst or ordering at a drive through. There are days that I just kick myself for not being able to express myself clearly solely due to speech blocks. It's maddening not knowing when and where disfluency will hit.