Your child is now into sports, academics, and other activities wherein he faces competition from his peers. He may lose at times and be sad but can now handle defeat in a matured way without affecting his self- esteem.
What you need to know
Reinforce on playing fair games and following rules.
When your child returns from a game, ask him, “Did you have a good time?” rather than asking, “Who won?”. If he says, “Mom! I lost the game”, you can say, “You tried your best. I am proud of you. Practice more next time and you will win. This way he understands its not all about winning only.
Never be rude to your child if he loses a game. Talk to him about the other areas where he does well. See ways of improvement than resorting to criticism.
Give opportunities to your child where he experiences winning as well as losing while playing. Gradually he will understand these outcomes are part of the game and if after losing he feels okay, it implies his sense of self esteem is intact.