stop lights to sensitive

if a barrel type switch, you can rotate it clockwise until the sweet spot is achieved..if a reed switch on a plate loosen the curved slot bolt, and push until correct position is achieved ~

First confirm that the lights are indeed always on. Check them while the car is off (key may need to be in on position on some cars). If they are indeed on, check to see if the brake switch is out of adjustment. The adjustment procedure is just as judge_roy explained. If its not the switch, then you have an electrical issue somewhere.

clearly the switch has a slot and setscrew---