I get it. And I'm really sorry that I get it because I didn't get it for so long (and there's a lot of other things that I don't get).
It is disappointing to feel sad for no reason. And I imagine it doesn't help when people tell you how awesome you are all the time. In fact, it probably makes you feel like you shouldn't feel sad, especially for no reason, which makes you sadder. Or more sad. Because that's the correct way to say that. Goddamnit.
I don't know anything about you other than what you've posted on your blog. And perhaps Google+, because I found that profile the other day and stalked you a little bit. But I very much enjoyed your blog. It seems like you and I created our blogs for very similar reasons... although yours was consistently funnier and had more pictures (and a cult following... if I have that no one's told me).
You could have a great job where people like your work and your personality. You could live in a destination city where the weather is perfect for most of the year and the landscape is beautiful no matter what. You could have (and probably do, if I recall that you have a fiance) the most wonderful person in your life who gives you space and cuddles when you need them. But you still get sad for no fucking reason. And it's awesome.
The good news, for me at least, is my sadness is only in passing. And it's definitely not the debilitating version you got. I've been reading psychology articles (for work) and the back of my brain is trying to self diagnose the rest of my brain, without my permission and even though I'm 99.9% sure there's nothing diagnosable about my brain. It's like when you hear the symptoms of a deadly disease that only occurs in one tribe somewhere in Africa and you think "I coughed last week! I have the plague!" and start planning your obituary. Except less extreme. I also have been fighting with hormones for months (well, years, really) and I'm convinced those boogers just like to fuck with you. Birth control is by design supposed to make it possible to have sex and not get pregnant (and various other medical benefits). Some types make women not want to have sex. At all. Which is fantastic birth control. I, however, have a secret weapon that my birth control is perhaps not prepared for, and that's a ridiculously sexy boyfriend. I usually win that battle. But I don't appreciate there being a battle in the first place. And although she's cuddling one arm at this very moment, making me get creative to type, the cat has been ignoring me almost completely. And it's not like she's a dog, where I could be annoyed or worried by her ignoring me, or even a particularly nice or social cat. She's a very stereotypical cat who hates pretty much everything, especially me. It doesn't help that I made her spend a week with a bunch of dogs. Oh, and my skin is trying to attack me.
You'll never see this, Allie, but I feel better having told you, kind of. I wish good things for whatever is going on with you and should you come back to the internet and give more pictures of your dog and the silly things that happen I wouldn't mind.
Until then, I get it.