I got "caught" yesterday. I was repairing a soybean platform, making a repair on a component I'd never had to repair. The customer was helping. The various pieces had to come apart in a certain sequence, then go back together not only in exact reverse sequence, but with certain of the pieces timed and indexed to achieve a specific alignment.
It took me three tries to get things put together right. Each time I goofed, I had to take it apart and start all over again. Even now, having done it three times, I'm not sure I could do it correctly in one try. I was annoyed, the customer was amused, but we finally got it together and working correctly.
The previous day, I tore apart a big, complicated variable-drive system and put it together in record time. Used several shortcuts that saved time, and would have looked like a genius if anybody had been around to watch.
The difference between the two repairs was that I've rebuilt dozens of variable drives, but repaired that specific component on a soybean platform only once. Mechanics may have special tools and enough experience to make lots of different repairs, but we don't inherently know how to fix everything that breaks. There are more than a few times that we're guessing or working "blind."
So if you're working on equipment, fixing something that doesn't want to be fixed and feeling a little overwhelmed...take a deep breath and proceed as a professional mechanic would: Draw sketches or take cell phone photos of things before you disassemble them; mark or number parts and lay them out in sequence as you remove them; practice-fit things together before assembly whenever possible; and, when things go awry and you can't put it back together correctly -- find a tech book or another mechanic to offer guidance.
I'll never be so bold as to say that anything can be fixed, because there are some things that just plain need to be replaced. But with patience, pluck and a big enough hammer, a person can give it a serious try.