Erghh...tough to answer because at 18 I know I didn't listen to many people...and I thought I was a "nice kid."

A lot of this stuff is learned through trial and error, and this saying (which has been attributed to many people from Mark Twain on down) is accurate:

“Good judgement is the result of experience and experience the result of bad judgement.”

So at least in this model, you have to go through the bad to understand the good.

I'll say this, from my own experience:

The time will pass.

In three blinks of an eye you will be 40.

I know it seems like a far away point now, but trust me, time accelerates as you get older.

Each summer you plan to learn how to sail a small boat.

Each summer passes and you have to work, you can't take the time off to do the course, the sunny days pass by.

Suddenly you are 30.

Blink.

The time will pass.

If you want to get good at something--business, music, art, whatever--start now. Persist. The time passes, quicker and quicker, whether you like it or not, and if you stick with whatever it is, you will develop that skill...

...and suddenly, in two blinks of an eye, you will realize you are a professional.

I have perhaps 25 functional years left in the workforce. The full force of this is in my face every waking minute. Be the person you want to be--or be a flake. That is fate's demand.

Don't be too concerned about money at your age. You can build it. Live beneath your means. I didn't, through my mid-20s, and it bothers me to this day. Put a percentage of your income aside every paycheck. Then you can take vacations when the opportunity arises, buy stuff on sale that you really want when it comes up, take that sailing course and get started on the road to enjoyment and perhaps mastery.

Don't let circumstances rule you. Need to get out of work early to take that course? Talk to your boss about it.

Start a side business now, if you're so inclined. You can make all the mistakes early and it won't cost you much...and you can be a pro at 28. Because, trust me, the time will fly by.

Make the things you want to happen...happen.

Don't be too interested in pleasing other people. It doesn't pay off. They will simply take advantage and then take more. Take care of yourself first. If a choice comes down to doing something you know is important to your life, or pleasing someone else and suppressing your desire or interest, choose yourself.

You can always get another job.

Speaking of jobs...don't let anyone tell you that "you have to pay your dues" or "you have to have more experience."

That is the Chicken Little way of the world and those people do not know what they are talking about. Someone told me I couldn't be a factory manager when I was 24. I quit, and within 4 months was a plant manager. People do not know what they are talking about.

Even me.

Trust yourself. Find your own truth. There are MANY ways to success--not just one. Not just the single one advertised on television. You can figure it out your way, and you'll probably be a lot happier.

Oh, and invest in some solid real estate as soon as you can to get a passive income going.