Ahh, youth. It's great and all. If it just weren't so tied up with the twin threats of "ignorance" and "inflated sense of one's own invincibility." When you are young, somehow you believe you will always be young, and if you are rich, you believe that it will only increase in frequency and magnitude.
Sure, I know there are those among us who are wise beyond their years. I was the worst kind of youthful ignoramus: I thought I was wise. My intelligence was indisputable, and indeed, I started racking up the financial windfalls. That first-year investment banking bonus that was equal to my salary -- I was 22 and full of such hubris. Indeed, the money was gone well before bonus season the next year.
And then came business school, with the promise of enormous salaries and the loan money that flowed like water. I'll never forget those trips I took (and I was one of the more economical among my classmates), London, Vienna, Ireland; I'll also never finish paying back my loans. Everything that I foolishly considered an "investment" is now proven to be more of a fast-depreciating capital expense; my expensive car, my gorgeous clothes, all that food, wine and travel. It was not worth it.
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Here's my advice, if you are in the position I was, once: don't live within your means. Live beneath your means (or else you'll be doing it when you, like me, are 35 and still paying off your youthful extravagance). Pick a salary that sounds sensible to you (and is at least 10% below the salary you're making) and tell yourself that's all you have to spend. Put everything else in a savings account and write yourself a note for 10 years from now. Put it in a safe place.
When you're in your 30s and a decade has passed, open the note. "You're welcome. Signed, Me," it will say.