Spent 6 months trying to fix my old car before a single test drive showed the real problem
I was set on rebuilding the carburetor on my '78 Ford, buying parts and watching videos every weekend. After months of work, I took it for a test spin and it still ran rough. My neighbor, an old mechanic, heard it from his porch and yelled 'sounds like a vacuum leak, kid'. I'd been chasing the wrong fix the whole time. Ever get so focused on one solution you miss the obvious issue?
Oh man, I've been there myself so many times. It's like you're staring at a problem so hard you forget to check the simple stuff first. I spent a whole afternoon trying to fix my washing machine because it wouldn't drain, only to find a sock had clogged the pump filter. Sometimes you just need someone to say "hey, step back for a second" before you lose your mind.
Stellas56 is right about tunnel vision. It's like your brain gets stuck on a loop and you can't see past your own idea. I've done that with house stuff too, trying to fix a leaky faucet for hours before realizing the shutoff valve was just old and loose. Sometimes you need that outside person to snap you out of it.