With her new role as country leader, the young princess has become very stressed out with trying to keep everything in line. She misses Celestia's guidance, and often finds herself reading through her old friendship letters. But, as stressed as she was, Twilight was a good, sane leader. Until she got thrown in battle. Eyup, one battle, one explosion, one Canterlot Castle turned to history, and BAM! Twilight becomes insanely paranoid, and ends up going crazy (and becomes future twilight...for some reason...?) because she lost her second home and one of her best friends in one battle (more about that on the pie sisters picture), sending the land into anarchy. She is eventually declared an unfit to rule, and is taken in by Fluttershy to recover, while Sweetie Belle takes over as ruler. Seriously, don't put your Twilight in a battle. It says so right on the box.