I’ve got many plans, and most of them revolve around not planning.
It sounds contradictory, I know, but it’s really not.
Consider this: it’s difficult to make yourself just jump headfirst into a new situation without working out some of the details ahead of time.
Where will I stay? Who will I talk to? How will I eat? What will I do for money?
All valid questions. All questions that you don’t need to answer before leaping.
Sometimes you are at a disadvantage by not having a plan. Some necessities are time-sensitive and you really do yourself justice by figuring out the details ahead of time.
Many decisions, however, are best made when you have the most information possible, and you won’t have all the information you could have until the very last second.
So from time to time, make yourself leap. Don’t worry about having a parachute or a way back up the cliff, just go.
The only way you’ll get better at improvising is by forcing yourself to do it. Start with smaller jumps at first, but do it consistently enough that you don’t lose your reflexes.
This way, if something happens to you that forces you to react impulsively and you don’t have time to prepare, you’ll be ready.
Also, it’s a hell of a lot more fun.
Update: December 11, 2016
Definitely not something I would encourage at all times, and some people will be more comfortable with this than others.
But perhaps especially if you’re prone to planning, it does help to train yourself to be at least base-level capable of improvisation. If nothing else, it makes you feel even more prepared when you’ve done some preparation, because if things go wrong, you don’t have to stress out over it; you’ll make it work.