It's not something you can force yourself through, unfortunately. The only way to get over VR motion sickness is to work up to it.
If you get motion sick after 5 minutes, spend 4 minutes every day doing basic things. After a couple weeks, you'll very likely be able to go about 10-15 minutes. So then spend 10 minutes every day.
The moment you get any sort of motion sickness, stop immediately. Nothing you can do will alleviate it and playing more isn't an option that day.
I do think most people are able to work up to and work through it, but most just try to brute force their way or expect that they'll immediately be able to do everything. VR is analogous to a craft, both vehicle and hobby. While you can just get right into a car or roller coaster and send it, chances are your body needs to adjust and learn a few things about it. And while you can just pick up painting right away, chances are you'll need to practice to learn techniques.
VR is very much a mix of both. Many people definitely can just get right on and pick it up pretty quickly, but that doesn't mean there isn't some amount of necessary adjustments.