I took an easy job (UK financial software) when I was downsized from a job that I loved (Embedded systems). I told myself I'd quit within one year and either move to somewhere else in the commonwealth (NZ, SA, Canada) or do a year of university in Sweden on a course I found really interesting, with a view to getting back to Embedded work. I did neither, and I'm still there.

I'm moderately well paid, I have a plan to save money + quit, I moved to a new country and now have a lovely girlfriend, so I'm still in a happy situation - but I wish I could have had these things and pursued my career a little better.