Just let them come, don't try to fight it. I imagine that you have tics when you block (contorting your face, tapping your foot, shaking your head, etc.). Stop them. You don't have full physical control over your speech, but you can stop these tics from happening when you speak. When I block I used to shake my head and contort my face trying to get the word out, but after I actively prevented myself from doing it, I noticed less tension and panic when I spoke. Even though I still blocked, I wouldn't look like I was having a seizure when I did and the block took the same amount of time to resolve. After a while you just stop blocking as much. At least I did. It might not help in the short term. Don't get discouraged. Keep speaking slowly and think about actively preventing your tics.