The father here in these verses of Proverbs is imparting perspective to the generations that follow him. In particular, he is continuing his teaching on the dangers of adultery and forbidden sexual relationships. He is telling his sons (all of his posterity) to listen to the perspective of an older man. They will lose so much life if they look for sexual fulfillment outside of marriage. Whatever pleasure they think they might gain will ultimately end in regret.
This is the kind of talk every parent should have with their child about sex. In Proverbs 5, the father makes it clear that sex is both powerful and good by design.