Panic attack, flying to South Africa from USA?

I've flown more than a few times and never had a problem. Until 3 years ago when I had a connecting flight, flying from Florida to Connecticut. That day was the first and last time I ever had a panic attack. On larger planes I've always been fine but for this connecting flight I had to change and get on a small plane, because the airport I was flying to was a small one. At first everything was fine. Then, BOOM out of nowhere severe turbulence. It was like the plane was struggling to stay in the air. And I was seated in the center of the back of the plane, i felt everything. My chest was pounding, I couldn t breathe, I was sweating and gasping for air. I literally started crying and praying. There was an older lady sitting next to me and we started holding hands and praying together. She was screaming and so was I. We eventually made it safely but I never got on another plane after that. January 2019 I'm flying to South Africa for my best friends wedding. Flight is booked but I'm literally terrified. And the total flight time is 14 hours. I'm not sure if I can handle it. I really want to go. This is my best friend since we were 2 years old. Anyone have any experience flying this long? Over the ocean. What should I expect? What can I do to prepare? I d love to hear your experience with flying long distance.

Sleep aid.

I fly overseas at least once per year and have never experienced turbulence as bad as what you describe. So your flight will probably be fine. But you might try some Dramamine, or talk to your doctor about getting one or two doses of anti-anxiety meds for the flights, just to be safe.

What can I do to prepare?
GO TO YOUR DOCTOR
Of course some random posting of I do this is FREE and most likely worthless.

Recently I took 7 flights on one trip from the uk to Hawaii, never experienced any turbulence and arrived safely from all 7 flights.

Really bad Clear Air Turbulence (you can look it up) is quite rare, often you might get a little jumpy turbulence, but this is generally short lived and the flight crew are always in full control.

Personally I would try not to think too much, I doubt medication is the answer, and your best thinking about how you are going to share your best friends special day.

This is why you keep your seat belt fastened. Screaming and crying gets you nothing, so stop with the annoying drama. Take a sleep aid if you want, so you don't bother the other passengers and will be calmer. Keep yourself otherwise occupied with reading, movies and food during your flight. I promise you aren't going to stay "terrified" for 14 hours straight; at some point you will forget about it and relax. It's not a big deal; people do it every single day. Your biggest worry should be that kid kicking the back of your seat, or the crying baby next to you, or the man in front of you who smells like he hasn't showered in 3 weeks. Focus on the fun you will have once you get there; it'll be a cool trip!