Once again, so much going on inside the music. Self-confidence, in particular, can be an under acknowledged backwater of the whole process. Confidence emerges from internal wilderness and yet it's often reduced to some cheap banner ad: "You just gotta be confident, relax." Hmm, ok. Makes me want to eat Wheaties and hope for the best. Meanwhile confidence involves so many components, belief and doubt chief among them.
During a recent performance, doubt rattled confidence and quickly came to dominate the tone of my musical experience that evening. Thoughts ran something like this... Terrible not what I meant to play can't stand my sound this instrument right now can't find anything just can't hear it hands like glue arms thick mud who is listening why did the guitarist just give that look why did I take this gig why am I here anyway heroes always believe triumph never sounded so bad and what's with the back ache etc. The spiral. It is difficult to interrupt, difficult even to name without a subsequent (unhelpful) flood of commands. Stop thinking too much. Quit being so serious. Relax.
One time an exasperated bandleader yelled at me across a stage because I as the drummer was rushing a tempo. He barked, "RELAX!!!" Irony fueled humiliation, music none the better. I don't remember what was happening with that tempo but I suspect self-doubt was somehow involved. On the contrary, the experience of thinking you played terribly and receiving feedback that you sounded great is one that most musicians know. I used to think that these periodic fits of doubt were symptomatic of a life phase or of skill level, that one day I might reach a state of unswerving self-confidence. Not so sure anymore. I find the internal volley goes back and forth, some strategies offering more ease than others in a given moment, no single approach yet to yield a cure all.