No matter what they say about happily-ever-afters, fairytales are always tragedies. There might be exceptions: everyone agrees that Cinderella really did live happily ever after, but having your mother and sisters murdered will do that to someone. Prince Charming didn't dare say a thing back to her or stand up to her, so she got her happily for ever and after. That's how it goes.
It's like Beauty and the Beast: he got it. The Happily(tm) was his, mostly because of the amount of drugs he dumped into her food every morning. The thing is, see, we're talking two different people. We're talking different goals and how people change and forget to tell each other they change. And we're talking about power. About what people want from relationships. About what they're willing to give. Power shifts, so Happily(tm) has to shift as well and that's what makes ever-after so damn hard.
And even if it goes well, even if you mesh together so that you're co-dependant on your co-dependence and there's no room in either of you except for each other: say you do that, and eve die together hand-in-hand – probably in a suicide pact – we all still die alone no matter who we're with. There are roads we can only walk along, and not even the magic of Happily(tm) with an overdose of Ever-After bolted onto it can change that.
Even magic doesn't last, but someone we think Happily(tm) will and if that isn't a tragedy than I don't know what is. Now I know what you're thinking. You think it's different for fairies when it's really not at all. I fell in love with a Brownie. Everyone said: a Pixie and a Brownie, really, but we had magic enough to stand against scorn. Until I made her brownies for our anniversary. Nothing I said would convince her it was a cake, that it wasn't her family, that I didn't want to cook and eat her.
There was a Brownie living down the road and she moved in with him days later. Word is she's happy now, even if it's not Happily.(tm) I haven't put real Brownies in my brownies. I never did. But some day. Some ever-after day, I just might find a new Happily(tm) all my own.