I also have motion sickness, fear of heights and falling and do not do roller coasters. I do TOT. It's not my favorite ride, but I'll tell you, I NEVER open my eyes, no matter how much my family begs, and there are handles on the seat. I grab those really tight so that I don't really feel the "falling" part, exept the elevator actually going up and down. I'm sure the people next to me think I'm nuts, but before the ride this time, I kept telling my hubby, "I hate this ride!!!" LOL
Why do I do it??? Well, it's hubby's favorite ride and he doesn't like to go alone and the kids were not there last time, so I did it. Like I said, it's not my favorite, but I tolerate to stop them all begging me and telling me how much fun it is. I keep telling them, "For them", not me!!!" They just don't understand. It took me a long time for me to actually try it, and like I said, it's tolerable. If I were you, I'd try it once, hold on tight if you're worried, and see if you like it. It actually wasn't as bad as I had feared and made it out to be, just not that much fun for me. I'm always glad when it's crossed off my list.
My family isn't really mean or pushy, but since they do allot of stuff for me that they don't particularly like, it's an "OK" trade off, that I can tolerate. Rollercoasters, no matter WHAT they say, "NO WAY!!!"