Respect your elders. Don't expect anyone else to support you. Maybe you have a trust fund, maybe you'll have a wealthy spouse, but you'll never know when either one might run out. Don't mess too much with your hair or by the time you're forty, it will look eighty-five. Be careful whose advice you buy, but be patient with those who supply it.
Advice is a form of nostalgia.
Dispensing it is a way of fishing the past from the disposal, wiping it off, painting over the ugly parts and recycling it for more than it's worth. But trust me on the sunscreen.