DD is 5. We play lots of board games as a family. We don't always let her win; sometimes I do, or give her a helping hand, and sometimes she genuinely wins outright (especially at card games and luck games).
This weekend I've noticed a few times that if she doesn't win she sometimes copes well and says Well done, but on occasion finds it very difficult, refusing to continue if someone has beaten her, taking/shoving pieces if she's annoyed and doesn't want to carry on...
I don't know what the best thing to do is - ignore, distract with a different game, cajole into continuing the proper way, refuse to play if she 'cheats'... Last one seems drastic but I'm not sure how best to proceed.
She is sometimes good at 'losing' and I know it's very normal, just want to help her learn good habits!