When it comes to disciplining your child, sometimes (many times?) we aren't sure if he just needs a talking-to, some time out, or if sterner discipline is required. One of the things to look at is whether the child is just being childish, or if he is being disobedient.
Childishness includes things like: forgetfulness; playing when he should be working; not following a task to completion; not doing something because of not understanding what is required (we adults forget that children don't always comprehend what we are saying), not getting ready fast enough when the adult is the one who is late getting everyone around.
Disobedience includes things like: saying "No"; stomping off; attempting to see just how close he can get to the line (yes this is disobedience and needs to be dealt with); deliberately doing what he was told not to do.
Understanding the difference in motivation may help you decide what action to take, or not take.