Paul Graham has this advice in his latest essay:
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.
When I ask people what they regret most about high school, they nearly all say the same thing: that they wasted so much time. If you’re wondering what you’re doing now that you’ll regret most later, that’s probably it.
The only real difference between adults and high school kids is that adults realize they need to get things done, and high school kids don’t. That realization hits most people around 23. But I’m letting you in on the secret early. So get to work. Maybe you can be the first generation whose greatest regret from high school isn’t how much time you wasted.