Mine is related, I believe, to my intense fear of humiliation and failure. I feel like I have come a long way in seeing myself as an actual human being, both dark and light; but I remember the worst times and those come into my mind also. Medication has done a lot to keep this from screeching out of control in my mind, but it still comes. I have been cursing myself as an idiot and a failure for ever thinking I could knit because I don't like the way my latest project turned out. I feel like it's idiotic for me to go home and work on my new project tonight after failing so utterly. I dread humiliation like it is some kind of soul-death. Nevermind that many of my projects have received a lot of complements. I feel like a fraud right now, someone that shouldn't even pick up the needles again; what would a REAL knitter say about this horrible sweater? And when I was young I might have thrown the sweater around the room screaming and ended up beating my head against the wall so I could focus on physcal pain and not the emotional kind (and because a creature like me damned well deserved it) before collapsing in tears; I heard over and over "what's wrong with that child?", from my parents.
I've got a good dose of OCD too, the kind that doesn't show as much on the outside (except for the tics I have learned to mostly hide) so what negatives show up in my mind tend to ruminate over and over. My therapist says to ask if "this is true" when that crap comes up and to counter it with something; which is how I at least rationally know that I've knitted projects that have turned out quite nicely.
With the OCD my brain is a battle ground some days, other days it's more like seeing ugly kites flying past and letting the breeze take them off to the edge of the horizon. I try to look for the positives, or a new thing, just move on. I will move on and keep working on my new project because to hell with it, if it's a waste of time then winter is a waste of time, can't do anything anyway. There always has to be an out, something to move on to. I have to try.