If you want to ruin your life, learn (1) statistics, and (2) design. Most things you learn are neutral or positive, but these two things will haunt you every day.
Early in my career I got to work with some amazing UX designers and researchers. I didn't know anything about design, and I learned so much watching these folks work. They relentlessly obsessed over friction and pain points. We embarrassed ourselves in user interviews where all our theories were disproven ("oh no, don't click ... why are you looking there!?"). The products we built were substantially better as a result.
But it started to bleed into everyday life. The door with the ambiguous "push", the basket handle that scrapes your leg at the grocery store, the chair that is just a little too high. When you finally see what it takes to make good design, you realize that *bad design is everywhere*.
Statistics is the same thing. Most people float around listening to folks who "have data", but the vast majority of analysis is deeply flawed. You misinterpreted the metrics, biased the collection, failed to control for confounders, or applied statistical tests wrong. If you get to sit on the other side of the table and critically examine the arguments people try to make with data, you'll quickly realize just how hard it is.
And then you get to quietly watch as people are swayed by the flimsiest of analysis with the shoddiest of arguments for some of the most important decisions. The data we have for trivial things? Perfect. The data we have for the most important questions about health and governance and hiring and management? Utter shit.
Ruin your life. Learn design and stats.