No matter how though a jet-lag can be, there are ways to make it less of a hurdle but most of the time I just forget to plan or do the things I need in order to function after a long trip. The main issue with me and jet-lag is that I love flying and don´t want to sleep during the flight. This is a bad idea most of the time and that is why its on my number one thing to do when flying or before. Get some sleep, sleep deprivation is not fun and affects everything so sleep and don´t think to much about the time in each place.
Drink water during the flight and sleep when you are tired. Unless you are on vacation, go to bed early and if you travel a lot, stop thinking about the time, sleep when you feel like it, it will help you a lot. The fatigue of travelling a lot are something to take seriously and skip coffee and alcohol. I am a coffee addict so for me it is hard to skip coffee but I try to keep it to a minimum during flights.
If you don't have noise cancelling headphones yet, that is a great investment for any flight you'll make. I use Bose QuietComfort 35 and those are really good. There is another pair out now that might be a tiny bit better.