I used to go straight for diamonds, without getting any other materials. (I quickly learned that I have to get wood first)
I also used to never use the shift key. (Lots of deaths)
One dumb thing I do today is filling a huge area with tnt, and lighting it. My computer hates it, but I have so much fun watching the lag.
And the dumbest thing I ever did: Stopped playing Minecraft for 2 years. (Missed the 1.8 through 1.12 updates)
