I only get travel sickness if I try to read something while I'm on the road, like reading a road map or a book. Otherwise I can travel for long periods with no problem, even on rough roads. I'm not sure about sea sickness though, because I haven't been on a ship or other ocean-going vessel in many years, but I remember having no problems with it when I was a kid (but it really was a long time ago, so maybe now I get sea sick now and I just don't know it).
I feel bad for people that get cripplingly sick during any sort of travel because I'm sure they're missing out on something. Traveling allows you to put yourself into a greater context and expands your understanding of cultures and societies and it's also fun and sometimes you maybe make a fren. Unfortunately traveling can be very costly and time-consuming, if it upset your well-being too then there's no doubt that traveling would be immensely unappealing.
Maybe one day I'll travel with a nenfren that gets travel sickness and I'll look after them and ensure they are daijoubu and that they arrive comfortably and safely and then we'd go on adventures.