I just wanted to comment that you are not alone here. I am 43 and have been building websites and web apps for over 10 years and always feel i am the slowest dev in the room. It gives me insane imposter syndrome and causes me extreme stress on the job. I spend hours after work trying to keep up on some projects and still feel my colleagues are running circles around me.

I'm not sure what the answer is, an came here hoping to find one, but I just wanted to say I'm glad to see I'm not the only one that faces this, and neither are you.