Fairly Simple. How much do you spend to maintain your lifestyle? What changes would you make to your lifestyle in the future?
As for me annually
Cars: Still drive a crappy car and don't have plan to upgrade, $2,000 on gas
Food: $3,000 goes to grocery, around $5,000 goes to restaurants
Vacation: None, work too much
Clothes: $3,000 on clothing, $5,000 is for watches
$42,000 all in, I am pretty happy with my lifestyle and don't think I would increase at least until I secure that $500,000 a year, that's when I would start thinking about having family and such.