My lessons:
- Invest excess money in a cheap index fund early and just leave your money there.
- Become frugal as a lifestyle. If you go up in salary over the years, but don't develop more expensive habits, you'll be saving a LOT. Thanks to this site, you know at least what you are saving for.
- Don't hang too long in your first job, where you were hired cheaply. Switch jobs and get better paid.
- Don't work too hard and get a burnout.
- Live a healthy life.
- Find a frugal partner/spouse. Beware spendypants partners.