To immediately think to not do something is often a reflex based on memory, and not a rational decision. Training reflexes is all about applying how the brain works.

Taking a hint from dog training, if you punish a dog too late, they forget what they're being punished for. Also the severity also doesn't seem to matter. Bad is bad no matter how loud or how painful, so just keep it to a minimum and have it for convenience. Beyond that rewards work much better for training brains.