Let's be honest, flying first class every single time would be out of limits and plainly unrealistic. I never find comfort in long plane rides thus I've come up with a list of things I do to survive it. I've been doing this since I was like 13. And yes, it helps you get through it.
1. Eat a healthy, filling meal the night before your flight and eat something before you board as well. If you starve yourself before a flight, you will just feel much worse and cranky all throughout the flight. Meals provided by the plane is getting better but never fulfilling. Pack granola bars, roasted nuts, dried fruit and whole-grain crackers. These are great foods that will help you feel full and they won't be confiscated during security. Also, it is a tip saver as compared to buying overpriced on board food.
2. Stretch out and shake it, shake it! Get out of your seat once in a while and sometimes move your arms and legs when inside your seat. You may look silly but arriving to your destination without the muscle cramps is well worth it. You could check some in-flight exercises here. Go to the lavatory, splash some water on your face and you will find that you will feel much better.