What's the worst that can happen if you make a five-year plan? That everything goes according to plan. While this seems counter-intuitive, thinking about what it means for your future to look exactly like you expect it to can shed some light on the values and dangers of planning.
If your life or business is exactly "on track" in a few years with what you expect it to be today, that means at least one of the following is true. Either you gained no new information during that time, which means you aren't learning, or you took no significant risks, which means you aren't trying. You may say, "I played it safe and stuck to the plan," but that only means that you minimized downside risk--and therefore minimized upside risk as well.
My favorite way to think about life and career is [that] the problem with having a
five-year or ten your plan is that you succeed. You look up and realize you're way off from where you should be because the world has changed under your feet. You were so dedicated to following through on something that you miss what's happening.
These thoughts were elaborated on more eloquently in the most recent episode, Exponent #53 (29:39):
If you think about the future and always make plans for the future, the worst thing about having a super-explicit five year plan is that you'll achieve your plan perfectly and then you get there and you realize that the world has changed while you've been focused on your plan. You realize that, yeah, you got to the destination you wanted to get to but it's nowhere near the place you're supposed to be. There's so much about the world that we don't control--basically everything--and the only thing I can control is me. And the only thing I can control about me is my actions and responses to whatever is happening right now.
The comments are in the context of education and career decisions, but are applicable more broadly. Both episodes--and the whole podcast, really--are well worth your time.