One of the most troubling aspects of VR sickness is that symptoms might last for hours or even days after usage . Most users who experience symptoms immediately after withdrawal from a VR experience still show some sickness, though at diminished levels, minutes later. Only a very small number of outlier users may continue to experience symptoms for hours or days. Similarly, some people who experience sea sickness complain of land sickness for extended periods after returning to stable ground. This corresponds to postural instability and perceived instability of the visual world; the world might appear to be rocking .