It's probably frustrating to hear me say that, because I haven't really answered the question. If you came to me looking for me to name a topic, you left disappointed. I've only converted your question into another question.
But I hope the new question is a more helpful one. What do I want to know twenty years from now? What kind of person do I want to be then? What would I like that person to remember?
This is a hard thing to do, to imagine yourself twenty years older than you are now. Twenty years ago my image of my life at mid-career was at best very vague.
But it does not take long to discover that for most of us life is full of very urgent pressures. Student loans come due. Our employers demand that we produce certain results that may be only indirectly related to accomplishing the goals we have set for ourselves. Paying my taxes doesn't directly contribute to my long-term plans except by keeping me out of jail. And if you marry or have children that, too, will quickly complicate your life.
I can't sort all of life's complications out for you, but I can offer you some advice: form a twenty-year plan. Take a little time, right now, to ask yourself: where do I want to be in twenty years?
And then do that again and again as often as you can for the rest of your life.
Here's the thing: don't worry about whether you'll actually get there. None of us can see the road ahead. At most, we see a few steps ahead and we guess at what lies beyond them. We are like travelers in a dark land, where the road is obscure and all we can see is the twinkling sky.
Well, then, pick a star to steer by.
It may be that you will cross one of life's horizons and that star will no longer be visible. Okay. But you can see it now, right? So follow it faithfully while it shines the brightest. Set a goal - I want to be out of debt, I want to be working with people I like, I want to earn enough to support my family and give charitably, etc - and then ask which direction you'll have to step in to move closer to it.
Because the alternative is that you will constantly be looking down at your feet, at the urgent matters of where to step next. And that is, after all, pretty important. You don't want to turn an ankle or step off a ledge. But if you're always looking down at the urgent things, your neck will bend and get used to that angle, and you'll have no idea where you're going or how you're getting there.
So look up, pick a star, and follow it. And then keep looking up.
A hypocrite is someone who tells you to do one thing while doing another. If you're wondering, yes, I have a twenty-year plan. And it undergoes constant revision. It's always changing, and yet, as I compare versions of it, I find that there are constant themes, like these:
* I want to be more in love with my wife, and to be making her glad to be in love with me twenty years from now;
* I want to continue to be learning new things;
* I want to live near my kids for at least part of every year;
* I want to earn what we need, and to be a generous giver to those who have a hard time doing so.
These aren't the specifics, but some of the general themes that keep emerging. One great thing about allowing yourself to revise your twenty-year plan is that you won't go crazy trying to do what turns out to be impossible. Another is that these patterns will emerge that will help you to know yourself and your deepest values a little better.
I am wishing you the best on your journey as I write this.