Hold down the start button to recenter your playspace. This should also buzz your watch and ask if you would like to do a full height recalibration as well. If you would like to navigate to a full recalibration manually you can do so via the watch menu > Settings > Experience > choose Recalibrate Room.
If you can't get your PSVR recalibrated to your proper height using the above recalibration options, you can wipe your saved info (which clears the calibration data) via the PS menu: settings > storage > system storage > saved data > rec room > hit options button > delete. The only data Rec Room stores here is your height calibration data, so there's no need to worry about losing any account info.