As parents we want to keep changing our children's behavior. We feel that the moment our child turns 3 and is over that whole terrible 2's phase, he or she is suddenly going to become a good kid. We keep waiting for them to change and stop throwing tantrums.
The truth is that every year our children will adapt new behaviors that you may not like. First it ll be the baby hood period when they need us every moment, then the terrible 2's, then they ll have the growth phase, then the preteens and the teenage phase and it ll go on and on, (until their frontal lobes are completely developed).
We are focusing on the wrong thing. We should be focusing instead on how to manage their behavior when they do behave in a certain way, and that is what will make all the difference in your child's lives and personalities.
It is not about whether your 4 year old says thank you and sorry enough times, to enough people. It is about whether this 4 year old kid grows up to be an adult who feels grateful, and is actually empathetic towards people. It is not about whether your 2 year old can regulate himself from wanting things inside a super market. It is about whether this 2 year old can eventually learn to be an emotionally resilient adult, and learn to manage his will and emotions.
We expect too much of kids when they are way too young. These mini versions of us are walking around with an underdeveloped frontal lobe and are not equipped enough to control themselves from wanting everything in a super market, or actually knowing that they need to be grateful or apologetic in a situation. It doesn't matter if they are throwing tantrums about things.
So what actually matters is how are you reacting or responding to that tantrum. You are a living, talking , walking e.g for them, from whom they will learn everything. So if you can be empathetic with them through that tantrum, and emotionally regulate yourself first. They will learn to do the same eventually. for themselves and others.
If you can set firm and loving limits for them when they are not capable enough to set those limits by themselves. They will learn about boundaries and freedom. So teaching kids how to behave ... its really not about telling them how to behave.. It's a lot about how you behave towards them and towards others in front of them.