Why would she talk about her exes more often regarding happy experiences, but not about sad experiences?

When it comes to sad experiences which she said of that she still needed to heal, she either wants to only talk about it to certain people alone, or when they bring it up, she goes quite silent and shy? I mean, she's been the one quitting her last relationship.

Why would she talk about her exes more often regarding happy experiences, but not about sad experiences?
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