Your first paycheck changes how you look at every price tag.

Money you earned yourself gets measured in hours rather than numbers. Once you know what an hour of your work feels like, prices convert on their own: a pair of shoes becomes a weekend of shifts, a night out becomes a Tuesday evening. None of that makes you tight with money. It just makes the trade visible, which it never was while somebody else was paying.

Price your next few purchases in hours before you buy. Some will obviously be worth it and some will not survive the conversion. Both answers are useful.