As people have already said, worry about getting sick and the psychological effect may make you more susceptible. There's no rule as to when you'll feel ill and when you won't. Take a sick bag or something similar if you’re worried about making a mess and keep it close to hand. If you do need it, you'll need it fast. But try & put it to the back of your mind.
In my case I don’t feel sick on rollercoasters or passenger jets but light aircraft has been a different story. About 5yrs ago as a back-seat passenger on a scenic flight (my first time in light aircraft - 172) I felt a little unwell but no accidents. Then about 2yrs ago I did a Tiger Moth aeros flight; someone else flying it, not me! The aeros were fine but on final approach I felt really sick. Even back on ground, I continued to feel like ****e. My balance was upset and walking felt strange.
Obviously aeros aren't part of the equation in PPL, but if you do feel sick, don't get in your car to drive home. Stupidly, I did, and things got worse, to the point where I stopped at the side of the road to force it up.
Problem solved.
I'm now a student pilot, four lessons in. My first lesson was fine until final approach (again) when I felt rough as guts. The guys told me later the feeling would ease the more flights I did. They were right. It's never been a problem since. Yesterday I was flying 30 degree turns, circling about 5 times in each direction and I felt fine.
The most valuable piece of advice here (drawn from my own experience) is to look outside as much as you can. You may be fixated a little too much on instruments at first (I was) but apparently this is a major contributing factor of air-sickness.
BTW, your first couple of lessons may all seem very complex but by lesson 3 & 4 you'll really start to feel you're understanding things better and your enjoyment levels will only increase!
Try to study diligently, regularly. Keeping your head in the books between flights makes it much easier to grasp things at pre-flight briefings and allows you to think quicker in the air. Right after each flight, go back to your Flying Training Manual (and BAK) to re-live your lesson by re-reading the corresponding chapter. It helps to cement in your mind all that you've just learned in the air, & it also helps you to more easily understand the theory. Lastly, concentrate on your flying but don't forget to savour the experience, have fun and stay relaxed. All this definitely helps your technique. Enjoy!
