I fly long haul a lot and am also fortunate to do so in premium classes. Second all the "what to bring" onboard tips and follow up with "how I fly" tips.
When I am flying east I will take a day flight and stay awake for the preceding 24 hrs (UK timings), so I am boarding the plan ready to sleep, and then wake up in the morning at my destination. I wear normal clothes to board and then after meal service, change into sleepwear (either pyjamas provided by airline or my own leggings and long sleeved t shirt - something lightweight, stretchy and limb-covering for the cold). I wear the eye mask and sometimes ear plugs, but I am used to plane noise now and my cabin is usually very peaceful.
I am usually woken up by the smell of breakfast cooking and then I get up, freshen up wash/brush teeth etc. Change back into travelling clothes, with fresh underwear.
Flying west I take a late night flight so I am already ready to sleep. If I have had to travel a fair way to the airport (or it's been very hot and sweaty), I'll use the showers in the lounge to have a good freshen up and put on clean clothes - it may be worth paying for shower facilities if you have similar circs. I then board, have dinner, get changed and do the same as eastbound flights.
I don't drink much. Sometimes a glass of champagne or red wine, but that's about it as it makes me sleep poorly.
If possible, investigate upgrades to business/first, if only for the ability to comfortably sleep your way through most of the flight and arrive feeling human. Lots of airlines now do a "bid" system where you can get an upgrade far cheaper than normal at the last minute. You only pay your bid if you are upgraded so you won't lose out and you'll still have your economy seat as failsafe anyway.
I always feel sad when I see nervous flyers - it is such a shame that you miss out on the magic of of it all. I hope you are able to get some help with your anxiety about it, because it really is stupendous to experience (I have been known to deliberately take an indirect flight just for the thrill of double take offs and landings!)