Have to agree with Wideboy, stock breaking and stopping a dog running into danger (like a road) both require something a bit more extreme (an absolute 'no') but if you have the bond established, they have a better reaction to your displeasure/command. I learnt alot from a dog we had who was 100% the pack leader but also a really nice chap. Watching him discipline a pup (and still have a bond with them, play with them, sleep with them etc) taught me what they understand and accept as a 'no' without being broken mentally by the experience.