You are some 2-3 km in the air. There’s nothing to hold on to. You are sitting on a piece of cloth that is barely large enough to accommodate you. No railings, no seatbelts, nothing to hold on to or stop you from falling to your death if the carpet gets into turbulences or a strong gust of wind makes you lose your balance. And let’s not forget that most depictions of magic carpet flights have the carpet move very erratically because they have a mind of their own.
Magic carpets are generally safe. It’s hard to fall and get hurt unless you’re stupid.
If it’s you doing the #levitation magic, it helps to focus on an object underneath you, like a carpet, a broom or whatever. Balancing on it is sitting on a pool floatie. If you got yourself up in the air and lose the carpet somehow, you probably have enough flying skill to land safely without one. Now, if you fly 2-3 km up and lose consciousness from lack of oxygen, you’re cooked, but that’s your own fault.
If you aren’t magical and the carpet itself doing all the work, then the carpet is your mount, like a horse. Well-trained mounts can feel the rider’s weight shift around and try to keep you seated. Just don’t make the carpet angry, or it might buck you off.