Are we talking self-discipline or child discipline? If it's child discipline... anything that even borders on violence is too much. And violence INCLUDES emotional abuse. Remain calm and make it CLEAR what your expectations are and what the consequences will be. Consequences should be age appropriate. Children respond best to positive reinforcement!

Being obsessive or violent in anyway. Get the point across and let it go.

When the cheeks turn for rosy pink to deep red or purple.

As for self development, self controls, and self discipline, there are no limits ... go ahead and push your self control internally right down to cellular level, you are allowed to command yourself and obey yourself as if you were both your own master and your own slave ... As for forcing others to learn discipline, the limits are actually very low, even excess repitition of verbal scolding can produce a resistance and rebellion reaction, which is opposite to the desired result ... and of course, as mentioned in some other answers, violent abuse and even psychological abuse are definately beyond the acceptable limits.

Are you asking as a father? You categorized this under Life & Society. Law Breakers generally need to be punished, but under the 8th Amendment the punishment must fit the crime, so people cannot be overpunished. I guess it's too much when the punishment is worse than the crime. Then education is beneficial but expensive, so you wouldn't overinvest in it beyond your needs for your career. Finally as a father (especially if you're hot tempered) you don't want to be a punishment to be raised by. It shouldn't hurt to be a kid. And all parents really need expert advice.

1) A little "c" more would be perfect... Sorry, I could not resist. 2) I found an interesting article about this, here an excerpt: "How much is too much discipline?" "Three years ago, the American Academy of Pediatrics condemned spanking, questioning its effectiveness and raising concerns about potential emotional side effects. Research has consistently shown that children who are spanked are more likely to suffer delinquency and depression, and to hit their own children -- and often their spouses -- as adults. Violence, insists Nadine Block, founder of Spank Out Day USA, begets violence. Murray A. Straus, author of Beating the Devil Out of Them: Corporal Punishment in American Families, agrees, adding that new research in behavior modification suggests that spanking "does not work any better than other modes of correction and control." Worse, he says, in the end, spanking "boomerangs and actually makes children harder to control and less well-behaved." Psychologist John Rosemond disagrees, writing in his book Parent Power! that it "is possible to spank a child well, to do it right and to make it work." Rosemond devoted a 1994 book to the subject, To Spank or not to Spank: A Parent's Handbook. "The problem with spanking," he writes, "is that most parents make a sorry mess of it."" SOurce and further information: http://www.wwrn.org/article.php?idd=9335&sec=31&con=4