The one-two punch of Luna abdicating the throne and alicorn!Sunset apologizing to her would shatter poor Celestia's fragile sanity.you know I can't help but think if she ever goes home she's going to make a heartfelt apology to her old mentor for being a brat. Her new mentor is rather brutally forcing her to deal with heavy consequences and learn the true weight of getting blood on her hooves.
Seriously, Celestia spend a thousand years waiting to be reunited with her beloved sister while singlehandedly running a nation of childish idiots, only to be rejected in a "you're not worth the effort of hating" sort of way.
Celestia: "Can this day get any worse?"
Alicorn!Sunset: "Hello! A space monkey god helped me become a better person, reaching out to me in ways you never could."
Celestia: "..."
Alicorn!Sunset: "Celestia? Are you okay?"
Celestia: "There is no Celestia, there is only SOLARIS, QUEEN OF THE ETERNAL SUN!!!"
Dragon!Grayven:

Quote of day:
"Always be yourself. Unless you can be a dragon, then always be a dragon."