I don't like the idea of plan B.
I'm the kind of person that has come to realize that it's better to take time making a good plan A, and revising it occasionally, than it is to have a bunch of plans distracting you. If you have too many plans, then you won't focus enough on them and may give up easy since you "always have a Plan B."
However, though I believe in this approach of "Plan A first", I do think that there's one thing your career does need: a Career Emergency plan.