The master cylinder should have enough spring to push the pedal back, if you have a power booster, it could be faulty. Also check all the pivot points of the brake lever and make sure it's not dragging on something. If you are using a pressure sensing switch for the brake lights, they turn on the lights at very little pressure. My truck would hold the lights on with just the weight of the pedal after stopping. I replaced the switch with an electronic micro switch, I got tired of pulling the pedal up with my foot. I also tried a spring to pull up on the pedal, it didn't help much.
