THIS! There was a local band here, their vocalist would ALWAYS be apologetic for their sound, vocals, tightness, delivery. Used to bring it up ALL the time. Used to frustrate me as if nobody had seem them before and had not formed an opinion, they'd probably go 'well I don't know what to make of them, but even their vocalist thought they were bad so I'm going to agree with him' best piece of advice I ever received was to never show any visual hint of stuffing up. 99% of the time the audience will only know from your visual queue, and they'd be more willing to forgive a slight mistake if you're putting 100% into it and creating a great live performance.