Hmmm, I guess one of my secrets is that I used my twin sister as a social crutch for so long that I don't know how to instigate or maintain close friendships on my own, and I'm starting to develop a sort of social awkwardness as a result, particularly now that I've been going to a different college than her and have been moving backwards in terms of social skills instead of the forward momentum I was expecting.
My sense of confidence, particularly as a musician, plummeted in college, as I constantly perceive every percussionist in studio as superior to me, especially concerning anything other than mallet percussion. I've had this mentality creep into my consciousness so consistently at some points that I experienced what may have been a form of depression; feeling constantly tired, uncharacteristically low self-worth, unable to find joy in the things that I love, and finding myself in tears when I found times that I was completely alone, while often holding them back when I wasn't. I'm just lucky that I'm too adverse to physical pain (and terrified of wrist injuries) to inflict any self-harm.
I also had a brief period last semester where I was starting to perceive myself as "broken" because I've never been capable of falling in love and have never desired sex. That mentality went away after realizing that I'm an asexual (and an aromantic one at that), but I still don't have the drive to tell most people about it because I don't want to risk being judged, especially by people I've come to trust, especially since it's such an obscure orientation and tends to require a pretty decent amount of time to explain and sort through all the intimate questions people ask about it.
Oh, and to top it off, I've never had a full reign on my emotions. I used to have small mental reactions that my body would overreact to, so I'd be a crying mess when I was mentally okay, but it's more recently evolved into having slightly more control of the bodily reactions while the mental reactions are much more out of control. I also don't think my body knows how to react to anger, because once I hit a certain threshold, my body defaults to crying, which is probably the last thing I want to happen when I'm in a blinding rage. I've considered getting psychological help for this, but my family still helps with my finances, and they're against the idea of me getting help for it (they think I'll grow out of it, even though I'm 19 and still have this problem), so I'd rather be interrogated by family about it.
You know, I didn't even think I had "dark secrets" before writing this since I'm such an open book to most people (partially because I don't know what's too personal to say in some situations,) and I go out of my way to be an optimist in most situations. Some of the people closest to me know about some of these items I mentioned, and a couple are ones I never felt the need to tell others about. I'm assuming that this post will incite a tl;dr reaction too, so I guess my "dark secrets" will stay as well hidden as a tree in a forest for the most part.