By Adam Jusko, ProudMoney.com, adam@proudmoney.com

When I was in my 20s, working my first “real” job, I thought I was rich (though I earned relatively little). I hadn’t moved out on my own yet and could buy more stuff than I’d ever been able to afford. Plus, I could still go out at night and party until all hours — I had the bounce-back capability of the young and my “real” job was pretty low in terms of responsibility.

I wish I had worked harder. And more.

Don’t get me wrong. I enjoyed my 20s and have great, fun memories. And I know no one on their deathbed says they wish they had spent more time at the office.

Still, I feel like I squandered an opportunity.

In your 20s, you’ve got a number of things that disappear or fade as you get older:

• Time
• Energy
• Lack of responsibility

You have the opportunity to do things that the man/woman who is married with three kids can’t or won’t do, whether that is a risky entrepreneurial venture or working 60 hours a week to get ahead in your career. When you are in your 20s, you don’t have the résumé of your older colleagues (or competitors), but you’ve got the time and energy they don’t. That is your competitive advantage, an advantage I didn’t see when I was in my 20s. I was metaphorically fat and lazy when I should have been hungry, when I should have been channeling my energies instead of being happy to be making more than 10 bucks an hour.