@Twiface
Outside of the guilt she felt over Luna and Sunset she’s pretty well adjusted.
Celestia’s personality changes a lot from season to season, depending on the writer. The mysterious immortal chessmistress sun-goddess of Season 1, who plays the long game and has plans that unfold over centuries, does not have much in common with the late-season Celestia who sits around the castle all day personally leading tour groups of schoolchildren and eating too much cake, and who has a crippling phobia of chickens. She can be nearly anything you want, to fit a story. Crazy Celestia can work well for short black humor pieces.
I’ve seen one at Spacebattles a few years ago where she has a terrible guilt complex and drinks way, way, way too much, when she’s alone at night, mainly about things that happened centuries ago but that still haunt her. Magical alicorn metabolism means this isn’t as unhealthy for her as it would be for a human, but it’s still an excruciatingly unpleasant learning experience for her worshipful Faithful Student to see her drunk to the point of incoherently wallowing in self-pity.