Marc Andreessen's first rule of career planning: do not plan your career.

It will waste your time and limit your career.

This does not mean you should not have a strategy. He goes on to say:

1. Instead of planning, focus on developing skills and pursuing opportunities. "I believe a huge part of what people would like to refer to as “career planning” is being continuously alert to opportunities that present themselves to you spontaneously, when you happen to be in the right place at the right time."

Take a portfolio strategy to your career. Every job has a potential return and risk profile. "The risk of any individual investment is not important; what is important is how the risks—and the potential returns—of all of the investment"

Once you start thinking this way, you can think strategically about your career over its likely 50+ year timespan.

Pmarca's Guide to Career Planning (and many other resources) can be found in the "Career" section of Long Form Reads