Praise your child, but ...
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Do not praise your child for the things that he does successfully for a long time. Mention the things that the child couldn't do but now can.
Do not praise for the things that should be a norm. If you admire the fact that your elder son hasn't struck a younger one for the whole day, then both children will feel that this behavior is rather an exception than a rule.
Take care of a praise formulation, form it so that the child does not doubt in your sincerity.
Do not conceal the bad sides of what and how the child did.
Allow your child to correct results of his actions. Do not shout: "Oh, you are such a blockhead ... again poured tea on the table!" Just give your child a cloth and ask him to clean the table.
Try to be tolerant when your child isn't able to do anything. When you're about to lose your temper, go away in another room and wait until you are calm. Do not forget to explain your child the reason of your going away and ignoring him.