The premise of the story is that this average guy who's hit a rough patch in life is given a pill that enables his brain to work at full capacity. He's able to think clearly, remember details from his past and put together connections that no one else is able to do. Without this pill, he slips back into the old Ed and loses all ability to function as he had before. But knowing what he is capable of when he's taking the pill, he continues seeking it out.
This is actually exactly what being on stimulants is like for me.
Without them, my brain is in a cloud of fog and fatigue. I can't think clearly, have trouble focusing, and if you're lucky enough, I may just fall asleep on you while we're holding a conversation (don't take it personally) (also, this has actually happened a few times. If you're reading, thank you for understanding, and I am still so sorry).
But within 10 minutes after taking a pill, my mind is awakened and I'm....well, awake. I can complete tasks, work efficiently, think critically, read and analyze. Comparatively, I feel limitless. But I can tell, within 5 minutes, of when my medicine has worn off. It reflects a physical change as well; my roommate/coworker can tell visually when they have worn off and when they kick on.
I'm not sure if there's a point to any of this (ahem...the last pill I've taken today wore off several hours ago) other than to say that if you want to have any understanding of how different my two worlds are, you should watch Limitless.
Also, my stimulants do not help me learn foreign languages fluently within a few days. Or create algorithms within the stock market to predict stock changes. Or know kung-foo from video games (because 1. we didn't have video games growing up and 2. that's just a knock-off from the tv show Chuck)