Not these days; under normal conditions speech happens quite unawarely, and any effort is focused towards not overthinking / overanticipating interactions. i.e. I try to relax, think of something else and then just "jump and do it". ​ However if feeling very tired, I enter into a different dynamic. I might start needing more concentration, experience more awareness, etc. Probably I'll tell my friend that I need some rest; I think it's bad to keep making efforts when exhausted. ​ I don't think I pick alternative words, since I tend to repeat phrases more than syllables, which is comfortable enough. ​ So, probably in general I don't think I experience tiredness as a consequence of concentrating during speech (which would be a good hypothesis anyway).