When playing, or perhaps I should say competing against Celestia, for it is never just a game with her. It is important to remember that even apparent mistakes on her part have been analyzed and thought out as much as ten steps ahead.
More than once in our eternal sibling rivalry has she purposely lost in a game we were playing. Using my overconfidence after a win as leverage to get ahead in other aspects of life I hadn’t even considered.
I suppose the best advice I can really give you is this: Do not play Chess with my sister.