Always be as kind as you can, but don't be a doormat.
Say "yes" more.
It's harder to shift arse fat when you get older, so don't encourage it by living in leggings and elasticated waists.
Don't feel you have to be in a relationship to be happy.
Travel as much as you can, while you can. See the world, if you don't fancy going on your own then go on escorted tours.
It's perfectly ok to stay in on a Saturday night.
Appreciate life. Sit in your garden, or on your balcony, close your eyes, breathe deeply and slowly and listen. Listen to the birds, kids playing, someone's dog barking, your own heartbeat.
Work provides money, so it is important, do the best you can. But it's not the be all and end all.
Do a bit of volunteering if you can.
Get a decent bra.
Get a decent mattress.
Work out what makes you happy, and be content to be yourself.