I left the PhD program after finishing my MSc and passing my qualification exam without trying my candidacy exam due to financial pressures. I could have easily scraped together enough with part-time jobs to solve the immediate pressing problems I had. While I certainly failed to finish my PhD, I would still be there today if I hadn't decided to leave when I did.

Other than the really obvious poor choices, it's hard for me to look back and say - oh yes, obviously that was a mistake and a failure! After all, if it was a choice - how can I predict what may have happened if I made the other decision? If there wasn't a choice, then it's not really a failure.