I think the solution is to work in the other direction. Instead of working back from a goal, work forward from promising situations. This is what most successful people actually do anyway.
In the graduation-speech approach, you decide where you want to be in twenty years, and then ask: what should I do now to get there? I propose instead that you don’t commit to anything in the future, but just look at the options available now, and choose those that will give you the most promising range of options afterward.
It’s not so important what you work on, so long as you’re not wasting your time. Work on things that interest you and increase your options, and worry later about which you’ll take.
“What You’ll Wish You’d Known,” by Paul Graham