Yes, don't feel bad.

I can solve advanced problems in a variety of technical, computing, and medical fields, yet simple bike maintenance continues to confound me. Even with the excellent online resources.

Theory is one thing - experience is another, and brains don't compensate for experience.

I changed my measly brake pads last month, thinking it would take all of 2 minutes. An entire hour later, I was still unhappy with how they were working.

Derailleur repairs are the same for me - I go in thinking it'll be a quick 10 minute job, and it often takes me half hour to get it to where I'm happy with it.

The ONLY thing that's been easier than expected was bar tape wrapping - that was surprisingly easier than the video looked.

It's the same with most things - if you both KNOW and have the experience of the "best right way", you can do the whole thing in a snap. However, if you just make one wrong move, even a slight one, your problems exponentially multiply. I think of it like getting lost on a 5 minute car trip - you'll NEVER get away in 6 minutes after a wrong turn - more like double or triple the time.