@jasminelei13, you are right, there are many other times during the day Jack could get off. However, given that Jack is complaining about his sleeping problems, I think that the sexual intercourse should be done at or close to, bed time.
You see JasmineLei13, when a male and female have intercourse, the male usually finishes first. Because of that our creator equipped males with an unique gland that produces a heavy sedative right after the excretion of the last drop of reproductive juice. This is a deep rooted self defense mechanism to prevent death by boredom, since the female will engage in mindless chatter right after the male retreats.
I am sure your parents will talk you through this at a more appropriate age.
I hope this answered your question, enjoy your stay here at lamebook.
PS Jasminelei13, please be careful on the internet. Even on this site, there are a lot of disturbed people commenting, so do not trust anyone. Imamofo, however, you can trust. I am sure he will do his best to protect you from harm, in his own unique way.