Staying in an unhealthy relationship
Hoping for a long-lasting relationship is not stupid, but staying in a relationship that is doomed for sure, has no future and is doing nothing for you betterment is a stupid move.
Spending money frivolously
Buying whatever you want, spending outrageous amounts of money is not going to fair well for you. Maybe now you don’t see the merits of saving as retirement seems something that happens to others.
Sticking to a dead-end job
Not spending money extensively does not mean that stick to a job where your heart is like, “Dude, enough already!” The 20’s are where you discover your passion and run after it not a paycheck.