What I should have quoted in my post on vanity:
It is a most amazing thing that young people never consider they shall grow old. I would, to young women especially, renew the monition of this anticipation every hour of every day. I wish we could make all the cryers, watchmen, ballad-singers, and even parrots, repeat to them continually, “You will be an old woman—you will” “and you.”—Then, if they have left themselves to depend almost entirely, as most of them do, on exterior and casual accommodations, they will be wretchedly neglected. No beaux will then draw a chair close to them, and sweetly simper, and whisper that the bowers of paradise did not afford so delightful a place.
–John Foster: Journal.