Recovering alcoholic here, I wish I'd have learned to fly sober when I was younger, I thought I enjoyed flying, turns out I was a nervous wreck and I just liked being drunk the whole time, and it was very acceptable for a long time to do so.

In the past 2 years I've been learning to fly sober, and it's boring and tedious, but very doable. You do need to plan in advance what you will do for 20 minutes 2 hours, 8 hours, etc. Never get surprised by idle time, which is everywhere.

I like to make up little games for myself. Create backstories for the other travelers, eye flirt with the cute guy, etc. But mostly just read.