I've had many people try my VR headset and people experiencing motion sickness is pretty common. However you can easily train yourself to delay the onset substantially, or even completely cure it. The best thing to do is immediately take off the headset, and orient yourself in the real world until the feeling subsides. Wait at least 10-15 minutes, or even better a full day before trying again, repeat until satisfied with the amount of time you can spend in VR. I've had friends who felt like throwing up after 5 minutes be able to enjoy the experience for hours after a week of this technique. Trying to push through it just makes it worse, and you will develop a psychological barrier or fear which can be very hard to break.