That for sure is a bummer. I have large shoulders and it would not matter if it was a pax or an attendant they always would bump me going by.
Anyway I find that what works best for me, and it may not work for you, is that when I am tired I go to sleep. If I am not tired I do not go to sleep. If I do not go to sleep eventually I will get tired and go to sleep and you can bump me all you want and I will continue sleeping - ask my wife.
The second thing I do is never ever complain or get mad or blame others about my inability to sleep, see above.