Well first I wouldn't say that meditation fixed the cognitive problems I had, but it did give me a little oasis of calm within a storm that was tearing me to pieces, which was important because it allowed me to begin the process of life/mind reconstruction.
Looking back on that time is insane. I was empty mentally, spiritually, a walking ghost, hollowed out, no thoughts, complete apathy towards myself, life and others. If I had died I wouldn't have cared in the slightest. My memory was fucked, I had no empathy, I could barely form a coherent thought, I had no self-control, was very erratic, when I wasn't apathetic I was either extremely depressed or manic, though the former was more common. I did nothing, was going nowhere. This was what got me started on my nootropic journey, and I think its an extreme case of a common theme on this site.
What really fixed my mind and mental facilities (and continues to) was neurofeedback, particularly Infra-low frequency and Theta-Alpha-Gamma Synchrony, which is the key backbone of my approach. Anything else I take is either for basic nutritional purposes or to supplement and enhance the gains from neurofeedback. I've been on that for about 4-5 months now (I think? I don't keep track of time much), and I'm still making gains on a session by session basis. The difference is INSANE. I can barely believe I'm the same person I was two years ago. I went from suicidally depressed to being the happiest most emotionally balanced person I know, from having no thoughts to being able to exercise my logical and intuitive faculties at will, regaining and probably even building on some of my former mental powers. My self-control is through the roof, used to be I had literally zero, I'd feel an urge and there'd be no counteracting force in my head to take consequences into consideration, now I reason out my actions and try to fit them around where I want to be, regaining the directional temporality which elevates us above much of the animal kingdom. I can learn so much easier, remember things that happen in my life, I'm way smoother socially, social anxiety is completely gone, now replaced with compassion and deep empathy for others... I can switch between play and seriousness at will and as desired in context, whereas before I was constantly serious. I've played guitar for a few years but recently my creativity has gone through the roof. I feel like I've literally gotten years better within the space of a few months, and I flow with and feel the vibrations so much more. This last thing is a theme which permeates my new life, everything is just more 'flowy'. It's difficult to convey except in the abstract. Like everything's just easier, not a chore, always enjoyable, I'm curious, I'm intrigued, I'm open, I'm integrated. I feel like the phoenix, completely reborn from the ashes of my former self.