Good explanation, makes perfect sense. The difference between my horizontal speed and the aircraft's was initially quite low, whereas my vertical speed increased very quickly."It looked like it had hardly moved forward"
N35, what you experienced is forward throw. When one exits a aircraft in flight, one is moving at the same speed of the aircraft. This is called forward throw. If the aircraft is moving at 120 knots, so you are you as you exit the aircraft. Your body continues to move forward as you exit and are out of the aircraft, until gravity and other factors such as wind get a vote in your forward movement. That is the reason "it looked like the aircraft had hardly moved".
And for note, "scared of heights" is a normal thing given to us from god, just as being thirsty is normal. What you felt related to heights we all feel. Congrats on feeling the fear and doing it anyways.
I'm sure I tend to be worse than average w.r.t. fear of heights, although much better than I used to be. I am near-sighted, though not severely, which was not identified in childhood; I went through school squinting and blinking, and finally got glasses when I was 28. Drove legally for 12 years without glasses until the world leapt into focus. Even now, I tend to only wear glasses only for driving or 3-season cycling - they are too much trouble for winter cycling.
I've since heard that near-sightedness is strongly associated with a fear of heights, which makes sense.
As well, my balance has never been very good, so all-in-all my fear of heights has probably saved me a few times.
As far as motivation, I was thinking about some stuff from my childhood recently. When I was about 4, I was out in the car with my dad. We stopped somewhere where they had a ferris wheel. It was quite small, with little one-person enclosed cages, so quite safe.
Dad asked me if I wanted to go on the ride, and I thought I did. I freaked out as soon as my cage started rising, absolutely terrified. The ride seemed to last for an eternity, with me screaming the entire time, and Dad standing there looking ashamed of me. I couldn't understand why he didn't ask the operator to stop the ride.
So, skydiving 24 years later to prove something? Perhaps ... sometimes it's hard to know what our motives are.