It's our Ears
The semicircular cannals in our inner ears to be exact. We got some sort of gel like liquid inside our semicircular cannals.
When we move, the liquid also move which help us keep our balance when we moves.
If we spin around with our body then we suddenly stop, we will feel really dizzy and we lost our balance. This is because when we stopped spinning, the liquid inside our ear still hasnt stopped moving, causing disturbance in our balance