People, especially young people, have no idea how precious and fleeting the pleasure of healthy sex is. It really is something to be savored, to be enjoyed to its fullest, and to be cherished. No rushing. No selfishness. A concerted effort to bring extreme pleasure to your partner.
It took me until my current age to really understand that, and now I've become a far better lover now than I ever was in my 20's or 30's. And in fact, this realization has injected new vitality into our sex lives after 23 years of marriage.