How do you deal (mentally) with a severe block?

How do you deal (mentally) with a severe block? I mean, when you are in a middle of a sentence and you have literally no idea how to get the next sound out of your mouth. I know, at *some* point, or maybe even quicker than you would have expected, the word will, somehow, get out, but in the moment itself, when you are expected to speak, and you are stuck as hell, what is going on in your head? Do you have any methods? Something concrete, that has helped you, at least to a point where you aren't so traumatized by it anymore? Something that can instantly create you a "safety net" for that moment?