1. Living within your means is the key, and it can be done at a fairly low income level. You have to be willing to identify and alter your most wasteful habits. For a while, I bought CD's of music that I used to like when I was in high school. But then I realized that I would listen to such a CD two or three times and that was it. It took me awhile, but now when I am in a music store and I see a CD from the Grateful Dead or Cream or whatever, I know that no matter how much I listened to that music back in the day, it would be a waste to buy the CD now. I think that if you are honest with yourself, you can identify things you could buy less of without suffering any real sense of loss.
2. Your human capital is worth more than your financial capital. Allocate your time accordingly. Certainly, you should not be spending 25 hours a month managing your stock portfolio (including tracking its value) and just 2 hours a month managing what you learn. One of the reasons for investing in index funds is that it takes less mental energy than trying to pick winners.
3. Change jobs more often than feels comfortable. You need to learn on the job, and the longer you stay in a position, the less you learn. Even within the same firm a change can be educational.