Your stamina regeneration bonus has a counter that won't reset as soon as you leave the resting area. It will leave off exactly where you left it. This means you could go buy pots and it won't reset your progress. You can leave the protection zone to do whatever you want, but it will keep the progress you've already made once you step back into the resting area your bonus stamina regeneration will continue as if you never left the zone. Even if you gain experience, the counter won't reset it will just make you lose 2 minutes of stamina for the creature you killed.