I spent four hours the other weekend trying to figure out why my toilet was leaking and dripping on the floor behind it (and doing water damage... took a while to notice it was happening). Well after four hours of swearing, I finally figured out that there was a hairline crack in a PVC pipe that shouldn't have had a crack in it... it was just fluke and desperation that I happened to look there.

The next day I added a ceiling fan in a room with a very old electrical box for the existing light... clearly not capable of holding up a ceiling fan. Another four hours of swearing to make that work.

Yeah, it would be faster to get a contractor to do these things, but I'm way too cheap, and they charge a lot for little jobs like that.