Eh, what can I say? It's a gift! xD



As for why these two broke up:



However much she doesn't want to be, she is, in fact, royalty - and a big part of what makes my Cadence who she is, is that as much as she tries to ignore that fact and separate herself from her destiny, she also doesn't try running away from it either. She knows that she can't. It's why she tries to hide her horn though of course she can't fully and staring in the mirror in the morning is a painful reminder that she can't. Ever since she ascended she's been set with a life path she's stuck with and a big part of her journey is carving out an identity for herself since all her life it seems as though she's had no control over her circumstances -

(she was abandoned by her biological parents, she was grounded because no one could teach her how to fly and that, combined with the casual racism she had heard growing up led to her being insecure about herself and after she ascended she had to go with Celestia, had to accept everything thrown at her, had to deal with being a Replacement Goldfish for Celestia (Celestia doesn't realize she treats her like Luna and not a scared angry child until it's too late) and had to be away from her family/thrown in a hostile environment where every step she took was scrutinized by absolutely everyone.) - ultimately all she wants is to just, at the very least, gain some autonomy and happiness. It's what she feels she deserves at the very least. Which is why she's such a wild and free spirit - it's a combination of escapism/burying her emotions and her own attempts to form an identity that's her own.



So eventually they break up simply because of the fact that they're headed in such different directions. He could never be happy being a Prince of Equestria (in the same way she isn't 100% happy with it even up to the present) though he would have done it to be with her and she knows that which does hurt for her quite a bit. It feels like another loss, though they remain as close as ever. Especially because while he could never be happy in her world, she would be more than happy in his, more than she is as a Princess. In short, he's kind of 'the one that got away' (I think there is a part of Cadence in the present that's truly still in love with both Big Macintosh and Prince Blueblood. They were pretty big parts in finding out who she was and I think there's also a part of her that misses who she used to be before assuming the throne. She's dealing with the situation to the best of her ability.)



In an alternate universe, she does choose to run away from everything and elopes with Big Macintosh to settle down on the farm and raise a child. Things don't go very well... not for these two and their relationship they're happily ever after but they don't call it destiny if you can just quit and the Crystal Empire suffers for her choice to cut off all contact with Celestia.