I did longhaul for 24 years. You can't practically, with a family, 'train' yourself in the days prior. Sometimes you may be lucky to sleep late or grab a nap before leaving. The long long flights have a 1/3 rest time. I usually used to find I could go long into the flight before crumpling, often a short period of extreme fatigue could be shrugged off and pass. Some people try and stay on UK time, but I always hated sleeping on sunny days, so I always slipped into local time with judicious naps.
I know it is difficult but that is just being irresponsible. Blackout blinds and sleep deprivation if need be to allow for proper rest prior to a scheduled flight. Well as far as the family goes, if they come first and prevent you from obtaining proper sleep, you should have taken the pay cut to fly smaller aircraft in the daytime. Aviation Induced Divorce Syndrome.