Proper technique is to give your body a break by getting off the saddle completely when stopped (i.e., straddling). If you can balance with your foot on the ground while remaining seated, you're doing it wrong. Most kids transitioning from training wheels to two wheels feel safer with the saddle set up too low, so that they can put both feet on the ground when coming to a stop. Too low saddle, in the long run, will cause knee pain. Leg muscles will not be fully engaged in cycling with an improper fit. You're not riding a Harley.