I have a history with this medication and other drugs to compare it to:
I used to take 300mg of pregabalin recreationally once in a while and for insomnia.
In such a sudden high dose it gives 1. a slight weird wired buzz after 2-3 hours like having a few weak drinks. 2. But in addition, it makes walking feel like floating and colors enhanced and slightly flashing. 3. A little dizziness and derealization too which I describe as the world seeming like a video game. 4. When closing eyes, I can still see the flashing colors. 5. It makes me feel both energized and tired at the same time thus helping with sleep. 6. Slight back pain reduction too. 7. It's something in between a weak hallucinogen and alcohol.
It makes me a little apathetic and reduces anxiety (like you said, devil may care attitude) but not much at all compared to an opioid high or a good full glass of whiskey, so I'm not tempted to abuse pregabalin as much as alcohol and opioids. Also, tolerance to pregabalin's mind-altering effects and side effects subside as quickly as opioids do.
As for side effects, the above mind-altering effects ARE side effects listed, but they subside after a few uses. I haven't had any other side effects than a little memory confusion. I eventually got it prescribed for anxiety 150mg in the morning and 150 in the evening but it doesn't do much except take very little edge off my anxiety. If I take the dose at once I again feel the above effects.