In some situations, there's not much you can do other than to just do your best to work through it. But I know that avoiding the stuttered sound and instead trying to repeat the word or sentence to get a running start to move through the block only reinforces me fear of the block. I've been having a difficult week with my fluency, but the other day I steeled myself, found a very low fear situation and person im comfortable with (my dad) and I had a conversation where I explicitly gave myself as much time as I needed to say the word without repeating or changing the word. Sometimes I would hold the block for a long time, but I just focused on moving to the next sound, vocalizing the next sound. After working through a couple tough blocks like this, I was able to feel a little more comfortable with the rest of them. It still took a long time and a lot of effort, but it wasn't as internally chaotic. The next day was easier.