I don't really get it no matter hard I try...
I live in NYC and fly to London quite regularly, I will pick flights that leave JFK late, fly J/F etc., wake up early the day I fly and find that the worst result is I might go to bed at 10pm on the first day in the UK.
I've done SYD-LAX-JFK in one day, leaving SYD mid-morning and arriving JFK in the early evening. Went to bed at 10pm and woke up without an alarm at 8am the next day. *shrug*