Like most internet commenters, I have horrible advice. Also like most internet commenters, I am happy to share it with you. (Nobody can give you advice like this. "What gives my own life meaning?" is a question that you and you alone are left with. Welcome to existentialism!)

For me, there are four questions:

- Where are my weaknesses/blind spots? You can't fix all of them, and I'll never be a good mechanic no matter how much I try, but my feeling is that you have to work on weak areas at least enough so that you are not cognitively crippled by them. After that you have to have a team to help you avoid problems.

- How do I really know what people need? Sure, I could read a Forbes article about a muppet shortage. It might even move me to give to a charity. I might then see all of my friends giving to muppet charities and talking about their plight. But what the hell does that mean, aside from the fact that if I announce I'm doing something about muppets I get a lot of positive attention? Which leads me to the next question:

- Am I in this for others or for myself? The important thing here is that there are no right or wrong answers. If you never work on yourself you'll be crap at helping others, so trying to choose "helping others" option is probably the wrong one, at least long-term. Best stick to yourself for a while. (Some people do this wonderful cop-out where they say "if I'm building something the market pays for, I must be both helping others and myself!". I don't disagree with this, but I think it dodges the question, which is probably more like "what can I do on-purpose for the sole benefit of others that will actually directly help them in a way I can understand?)

- How am I sure I am exposed to enough in life to actually make a good choice? If you know nothing, run across somebody who needs a piece of bread and give it to them, you've picked a problem and solved it. If you know somebody who dumps high-quality food every night and drive a truck from their spot to a place where hundreds can eat, you've done the same thing -- but it helps more because you know more. So how are you sure you know enough to not waste your life giving out pieces of bread to 1500 people when you could have taken the same amount of energy and fed 1,000,000? That's the crux of the thing, at least for me.

I spent my early life working on my weaknesses while learning a lot of technical stuff. Then I switched off to working for the highest rates possible, traveling all over the world meeting people and solving whatever problems they had, not worrying about my own. I used the market to help guide me to people who were in some sort of distress. Then I looked for patterns and root causes.

As I was doing that, I went back and deepened my education in the liberal arts: philosophy, rhetoric, writing, understanding and appreciating various forms of art, and so on.

I am happy where I ended up. I am also content in knowing that I couldn't have short-circuited it by trying to "jump ahead" and solve world hunger at age 20. There are probably a bunch of folks out there who could do this. From observation I have found these people are 1) extremely smart, and 2) profoundly ignorant. They don't know a lot of stuff and they're happy not knowing. They just have problem X they are going to solve one way or another. I was never happy not-knowing, so I had to work it all out on my own.

ADD: Once you decide, of course, there's actually making it happen. That's an entirely-different question. You could decide the right way to cure cancer. You could know enough to come up with a cure. But that doesn't mean you can get anybody to listen or actually make a difference. (grin)