I don't think the problem here is standards or seriousness.
It's okay to have high standards and to take your work seriously and want your work to be good. But that doesn't mean Literally Everything That Exits Your Pencil Should Be High Quality -- quite the opposite, in fact; if you want your work to be good, you have to be able to produce A LOT of bad work -- crappy doodles and off-model studies and bad sketches and "finished" attempts that didn't quite make it. Not everything you make will be something you're proud of, but it's all a stepping stone towards making the work you want to make.
If you sit there not finishing anything until you can make good work, you will never make good work.
High standards and taking your work seriously means that as you produce things, you evaluate them critically and determine whether they're up to your standards, and what you need to do better for your next piece, or on a rework..... not that you fail to produce things out of the fear that they'll be bad, or that you berate yourself when you produce things that are only part of the way there -- a necessary step of the process. You aren't describing high standards.
The problems you describe sound like they'd be more usefully tackled by a therapist than an art instructor. And I don't mean this pejoratively!! I have symptoms of Obsessive Compulsive Disorder -- not the hand-washing/door-locking stuff everyone's heard of, but the weird kind that sits in your head and makes you paralysed with fear and guilt over innocuous things that are somehow your fault -- and just, finding out what it even was, and having a better idea of how to approach those thoughts when I'm assaulted with them, helped me so much.
I don't know you personally, so obviously I can't say for sure, but it seems like this is coming from a deeper place than artistic standards. And while believing the lies that your brain tells you is obviously unhelpful and makes your life miserable, makes you unable to move forward and do the things you love with joy....... berating yourself for having those feelings is equally unhelpful, and I think a glib response of "you're just taking this too seriously" isn't the right answer either when you're being guilted and bullied by your brain for every step of the process.
You gotta be able to recognise the lies and the bad feelings that your brain gives you for what they are and realise that they don't reflect reality..... while also accepting that they're there, and not holding it against yourself. You gotta be able to see that producing a bad sketch is not a disaster, while also not considering yourself oversensitive for feeling like it's a disaster. Be kind to yourself!!