In 35 years of flying I never once managed to sleep on a plane until last year when my TA booked me on a couple of TATL flights, Business class. It's not just that the seats are bigger and they lay flat so you can sleep; it's also because the seats are farther apart so it's quieter and you feel like you have your own space and they pamper you more, and you get to use the Business Class lounge instead of the usual waiting area. It really made the entire experience more relaxing and pleasant.

It's a TON more money but I'd give it a try just once and see if it makes a difference.