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