I feel like I've seen quite a few posts talking about imposter syndrome and how it effects most people, in like a "dumber/ less qualified men than you have done it" kind of way. And this is true for almost everyone!
But I haven't really heard much discussion on here about how imposter syndrome effects musicians (specifically conservatorium students lets be real). Because I've had experiences where that anxiety voice was right! Sometimes you're not that good, and you sound bad!
It's a bit difficult when a lot of advice you've heard about a type of anxiety centres around that anxiety being irrational - when actually what you are being asked to play is beyond your current level and so your anxieties are being validated by real world failures.
Anyway what helped me was to sort of 'yes, and' that anxiety voice in my head. Like "yes, I am in this one moment unable to play x part" but really fast instead of spiralling I try to get in there with "AND SO I will remain patient with myself and go back to the absolute basics, practicing so that i can play it very slowly line by line (yes I only have 4 days until the concert, that is fine, I will pick just the most exposed parts first.)"
This type of thinking has helped me, because I was just shutting down whenever presented with the possibility that I'm not that good (& therefore what was I even doing there, who let me in to study here ect. Ect.) So accepting that FINE maybe I'm a bit shit actually! Has helped me actually work on areas where I do sound pretty bad, rather than avoiding them out of fear of... sounding bad. Like I'm going to sound bad either way! Also playing with intentionally terrible tone, like the worst I can make it, then sort of 'stepping backwards' until it sounds good has helped a lot in teaching me that it's not that serious & I'm allowed to make bad sounds (and actually it is imperative to make bad sounds if you want them to become better sounds).
Anyway this is really informed by our wind band having 3 week turn arounds for concert programs (which I've never been able to handle lol), and I got promoted to 1st for the first time and GENUINELY nearly had a nervous breakdown ahaha. ANYWAY it is infact possible to improve your playing! But not if you can't face your weak spots!