Back in 1980, against the advice of all who knew me well, I started a PhD. After doing all the necessary work I got bored and, like many research students, struggled to write the thesis. By 1984 I had pretty much resigned myself to not completing. Then I got a bossy girlfriend who convinced me that if I didn't finish I would spend the rest of my life regretting it, so I buckled down and wrote up. About ten years later my teacher took me aside and we had a little chat:
"Finishing that PhD was one of the worst decisions you ever made."
"Why's that?!"
"Because it's put you on top of something you may never climb down from."