I was giving my car a tune-up yesterday. I’m not super handy with cars, but I can change spark plugs, oil, etc… I stopped by an auto parts store, picked up new spark plugs and then got started pulling out the old spark plugs. That is when the problems started. I couldn’t get the old spark plugs out. The 5/8 inch socket just wasn’t catching. The spark plugs are a few inches deep, so I couldn’t see why. I double checked the socket size on the new spark plugs and confirmed that was right. I tried to get the spark plugs out again, but no dice. Something was off.
I headed back to the auto parts store to talk it through with them. They looked at me like I’m and idiot and told me to use a 5/8 inch socket that was deep enough to catch the spark plug (a.k.a what I was already doing). Frustrated, I headed back to try again. The 15 minute job is pushing an hour now and I had beers to drink, but I’m stubborn enough to not give up. I get back after it and still nothing. Something isn’t right. Then it hits me, why the hell are we using 5/8 inch on a Japanese car? So I try the closest size in metric and still nothing. Stubborn as hell and thirsty for some beers, I dropped down to the next metric size, and boom, the plugs come out with ease. I had been basing all my assumptions on the replacement plug size, but it turns out the auto parts store gave me the wrong part.
I was working off bad information and it caused me great delay. When making decisions, whether it be in investing or something else, you need to act like your assumptions might be wrong. Constantly ask questions of yourself and your assumptions. Don’t be overconfident in your assumptions, because often they are wrong.