Chill out. The photo you've posted is not of a seat in row 31 on a 77A. I know because I've sat in them before. The door is designed differently and you'll have plenty of legroom. I'm only stressing this so that anyone else stumbling across this thread won't panic due to an inaccurate description.

I do exactly this trip several times per year in Y. Many posters here do it more often than I do, also in Y. Is it the most fun thing in the world? Of course not, at least for me. But we survive. The key is expectations. If you board the plane convinced CX have cheated you into buying this seat (they haven't); that you have the worst seat on the plane (you definitely don't); and that the trip will be "agonizing" (it doesn't have to be), of course you'll be miserable. Even if you end up hating the seat because it doesn't have a window, it's only 16 hours out of your life. Sit somewhere else next time.