If I had learned how to fix my own heating and cooling system.
I would have been able to save a lot of money over the years, and not only that, I would also have a nice sense of accomplishment by fixing my own air conditioning or heater.
I realize that not everyone is cut out to be able to install plus repair air conditioning, although I assume if I had learned when I was younger, I would have been able to do it. I may not have decided to be a heating and A/C professional for my main source of income, although I also could have used it as a little side hustle. Between fixing my own heating and A/C when it has broken down throughout the years, plus also repairing the heating and A/C units for other people as a moonlighting job, this would have entirely helped me financially. The guy that came to fix my air conditioning not too long ago had to climb up into the attic to deal with whatever the problem was. Ironically the guy who fixes the AC has to practically pass out from heat stroke because of the sites he has to go and crawl into. Then at my other house when I needed air conditioning assistance, sometimes they had to go under the crawl space of the house. That too is truly hot, plus it may have even had the skeletons of outdated disgusting critters that died under there as well, not to mention truly dangerous spiders! My point is, being the AC guy is not all glamorous and everything, but it pays well plus it also can save you money if you can repair your own heating and cooling system.