It's all Specs' fault.
After the Tirek incident, you were tormented for months by the fear that you might do something that spectacularly stupid and harmful to your friends again. You tried getting yourself turned to stone again, but your friends put a stop to that, and convinced you it was a bad idea anyway. But you were still afraid, because you do stupid things all the time. That's part of what it means to be Chaos. You can't possibly think through all the potential consequences of everything you do, because if you did that, it wouldn't be chaos. Still, after you royally piss off Fluttershy by getting overly jealous of her new friend, you're tormented once again by nightmares of alienating all your friends and losing them, or alternately of being too subservient to what they want or what Celestia wants and losing yourself. It gets to the point where you actually need to break down and accept help from Luna if you're ever going to get any sleep again.
Finally, you remember the technique Pinkie uses, that she told you about years ago, when you were first let out of stone. She splits off tiny portions of herself to be non-chaotic, and has them live in her head, doing the jobs they need to do because Pinkie doesn't have an infinite supply of chaos magic and needs to employ things like logic and preparation to make what she wants to happen, happen. You've always made copies of yourself, but generally they're either remote puppets that you're controlling, low-intelligence programmed constructs designed to wield your power in specific ways you've pre-defined, or you've literally split your consciousness into two bodies and your single ego is operating both bodies equally. You've never tried to literally make an aspect of your own personality into an alternate self with its own mind, like Pinkie did, and when she first told you about that the thought terrified you.
For a creature of Chaos there is a lot of stuff inside you that you prefer to repress or redirect. You pride yourself that you're not evil, just chaotic, and that anypony who called you evil just hates chaos... but there are impulses within you that could be evil, if you let them be. You don't like the face of chaos represented by war and destruction and death, but it's part of chaos and it's in you as much as all of the more wondrous parts of chaos are, and if you'd made Discords to represent parts of you that you yourself don't want to be, wouldn't they end up being those darker parts? And then you'd have to fight your evil alter ego and that never ends well.
But now, you realize, there is a part of you that you would rather externalize into another self. There's a part of you that cares so much about Fluttershy, and to a lesser extent your other friends, that you'd give up chaos if you had to... and you don't want to give up chaos or even think about it, but that part exists. That's the part that tried to have you locked away in stone so you couldn't harm your friends, the part that causes your recurring nightmares of screwing everything up and losing them. You don't want to be that part of you because that's where the other nightmares come in, the ones where Celestia has you working as an accountant or where Twilight is making you sort books for her and you lose your powers and your self and sometimes in the dream you feel like you're fading out of reality. But that part of you needs to exist and have a voice, but it can't be the boss of you either.
So you make Specs. Your first fully realized Other Discord, the way Pinkie has her Other Pinkies. You give him glasses to distinguish him from you, and you make his primary mission to think not about chaos but about your friends and how to keep them. You know yourself to be smart, cunning, manipulative and quite capable of using logic if it suits you; you just don't like it. You don't like to coldly reason things out because that's not chaos and you feel like if you did that all the time you'd lose yourself. So Specs by his very nature is less powerful than you; he can't wield chaos to full effect and take you over or control you, because he's not nearly as chaotic as you are. He can't actually understand ordinary ponies any more than you can because you can't give him a trait you don't have within you, but he can use logic and observation to figure out what they care about, whereas you can't be bothered because caring what ponies care about is antithetical to chaos. And he can give you advice, but if you decide the advice is bad, you can make him go away.
And he works well for you. You don't ask his advice about Spike and Big Mac and their stupid Boys' Night Out, as if you really want to hang out with sidekicks and background ponies, but after they admit to you that your contributions would be awesome if they weren't so terrifying, you get Specs involved and he helps you plot things that won't actually terrorize your friends completely. Before long you have Specs GM'ing games so you can play as Captain Wuzz and be as taken by surprise by random monsters and plot twists as any of them, and while Specs isn't nearly as creative as you are, apparently he's a lot more creative than Spike – a thing Spike himself admits to you, acknowledging that the games your alter ego runs would be cooler than the ones he ran even if your powers weren't involved. You don't want him taking your friends away from you – the fact that he's more capable than you are of understanding what ponies like means you're honestly afraid that if you let him interact with your friends without you, they'd all end up his friends instead and shut you out – but he knows everything you do, so you can pull him out to ask for advice on something they said or did or something you should or did say or do, and he'll know what you're talking about whether he was there when it happened or not. Occasionally you let him sit in on incredibly boring meetings that Celestia for some reason wants your input on, because he hates them too but he can put up with it, being more logical and less chaotic than you are.
You never expected that he would almost get you killed. Although it's not really his fault; it wasn't like one of those "creation turns on creator" totally clichéd stories that you'd have had to destroy him for if that was the case just because of what an overdone trope that is. He did exactly what you made him to do; you didn't know that what he told you to do could literally end your existence, so he couldn't possibly have known either. Although you'd always had dreams that implied it, but you'd never had enough reason to betray chaos that you'd tested it in real life, and you can't remember any other avatar ever doing so either, so you didn't have any reason to know it could literally be true. After all, you used to have recurring nightmares about being forcibly turned into a pony, and now you can turn into a pony anytime you want and it doesn't have any effect on you at all aside from sadly making you somewhat less handsome, so why would you think the dreams of being forced to embrace order and subsequently fading away were actually a thing that could happen?
(Besides, you're the one who let it happen. Specs made the suggestions, but you're the one who sat there with it happening to you and did nothing to stop it, and that's the thing that terrifies you the most.)
Notes: The name "Specs" for Discord's alter ego comes from discord-trolls on tumblr, and the name seemed better than anything I could think of, so I borrowed it.
The story deals with the concept of being suicidal, which you might possibly guess if you watched the episode - or at least, the concept of giving up and letting yourself die. It also explicitly states Discord's interest in Fluttershy to be romantic as well as friendly, though at this time Discord has no idea whether this is reciprocated or not and thinks probably it's not.