I need medication for anxiety and depression but I don't want it to change me

I hope I'm posting this in the right place. I apologize in advance for being vague but I don't want to reveal my identity.

I suffer from severe anxiety and depression. I've seen a doctor and could've been prescribed medication but chose not to take it. I work in a field where I have to do a lot careful observation followed by critical thinking and evaluation. I am widely considered to be one of the very best in my field. Like 99.99 percentile good at what I do. My worry is that if I take the medication it will change my brain to the point where I'm no longer able to perform at the same level. I know this probably sounds silly, but from my understanding the medication does alter brain chemistry and I fear that my new brain chemistry will yield different results.

Am I being ridiculous? I know the medication doesn't slow you down or make you dumber but even a small decline in my performance could be very bad for my career. I just want to feel happy and normal but don't want to change who I am.