Fourteen hours in economy is a lot more bearable if you pack for three things: sleep, power and water. Everything below fits in your personal item, so you're not standing up to open the overhead bin every time you want something.
Sleep: the upgrade you can actually afford
The classic U-shaped pillow has one flaw: your head drops forward the moment you nod off. A memory foam neck pillow with chin support fixes that, and one with a washable cover is worth it after a long flight. Add a contoured sleep mask (the shaped cups don't press on your eyes, so you can wear it for hours), because cabin lights and the seatback screen next to you will stay on longer than you'd like.
If you buy one thing, make it noise-cancelling earbuds. Engine drone is what makes long flights so tiring, and cutting it means you can keep the volume down and actually sleep. Charge them before you board; you can't recharge a power bank on international flights anymore.
Look after your legs and your water
Many long-haul travellers wear compression socks (graduated, 15–20 mmHg, sized to your calf) to cut down on swelling. Walk the aisle and flex your ankles every hour or two as well, and if you have a circulation condition, ask your doctor first.
Bring a collapsible water bottle, empty through security and filled at the gate. Toronto, Montreal, Calgary, Vancouver and Halifax all have refill stations, and the crew will top it up during the flight if you ask.
Make security painless
Liquids in your carry-on must be 100 ml or less, all in one 1 L clear bag. A sturdy clear 1 L toiletry bag survives a round trip far better than a sandwich bag. Prescription and essential medicine is exempt; just declare it at screening.
Habits that help more than gear
Pick a window seat to sleep, an aisle seat to stretch. Request halal, vegetarian or other special meals at least a day before you fly. Set your watch to your destination's time when you board and sleep on that schedule. And pack a change of clothes in your carry-on, because the one time your bag is delayed is always the long trip.