Best items for very long flights?

Next week I will board onto one of the longest commercial flights in the world (Mexico City to Shenzhen) at an eye-watering 17 and a half hours of duration, and wanted to know which items may help me to make this flight a little bit more bearable...

I currently have:

- Power bank

- One of the best noise cancelling headphones available (Bose Quietcomfort Ultra)

And that's pretty much it. Any suggestions?

Edit: the longest I've flown was 3 and a half hours, so I haven't experienced at all any flights like these.

Edit 2: for anyone seeing this, my flight is over and it was a pain in the butt (quite literally). It was sooo boring, but compression socks made it a little bit more bearable and I REALLY appreciated the fact that I had my row completely free, so I could lay down on the sits.

Total flight time was 21:30 hours, 3:30 from MEX to TIJ, 2:30~ hours inside the plane and 15:15 hours from TIJ to SZX.

We will see how my return flight in 2 weeks goes.