This is encouragement to not make threats you’re unwilling to follow through on. Saying, “If you have a messy room, I’m not buying you any more toys or clothes (Guilty!)” is not an honest threat. “You’re grounded forever,” probably won’t happen either. Be willing to choose reasonable consequences you will follow through on, and your child will believe you and behavior you desire will fall in line more quickly.
This is so true, and remember not to let them negotiate! My son’s now old enough to do that and will usually end up pleading not to be “punished” because he’ll be good the next time.