I was just on a plane like 2 weeks ago. I fly a lot, and often on really turbulent flights (I won't tell you which are most likely, as specifics on this site tend to do more harm than good). The only moment of panic for me was when the woman next to me pointed to this woman who'd been uncomfortable through the whole flight and asked "Did she just get sick?" I thought my heart had stopped for a moment, but I looked over and she was just grading papers and had her head down.
If you have to pee often, sit in the aisle. If you never have to pee on planes aim for a window.
Obviously try to avoid a middle seat unless you're sitting next to someone you know. Sometimes they will offer the extended leg room sections for a VERY small fee (like $25) and if they do, you should take it. If the exit rows are still available, take those seats as they almost always have more legroom. Sometimes it's a LOT more, like more than first class. Over the wings is the least turbulence.
The Xanax will totally eliminate the anxiety. I took one once before a horrible flight (one of the most crowded travel days of the year, very long flight, all sorts of horrible things) and I didn't even feel any pangs of fear, I was as calm as if I'd been sitting in a lawn chair the whole time, seriously.
Jet lag isn't an illness, it's when your sleep schedule is off from a time difference.