There were times when Rainbow Dash used to feel like she was her own worst enemy. I guess this couldn't have been helped, really. A life lived at the top of her game was a lonely one, and so she had plenty of opportunities to overthink the matter.
Several times as of late when I've spoken to her, she's gone on rambling tirades about how “awesome” and “uncontrollable” a mare she was in those days. She boasts about that time in her life, only because she can. It's not that she was happier then, but I think it's because she desperately needs to excuse the things she did and how she went about doing them.
Honestly, I think Rainbow Dash—even after all these years—is having a hard time coming to grips with just how much... happier she is, as if her entire life has to be one uniform emotion. It's one of the many things that I still find endearing about her. Beneath all of the boasting and showboating and daredevilish spotlight hugging, she's really the most selfless mare in the world.
And though she'll never admit it to my face, I can tell she's the most sensitive and clingy pony in existence, which makes me all the happier to know that—these days—she's got that very special somepony to cling to.