Drugs significantly alter cognitive processes and perceptions. I know that reads like a duh comment because that's literally why people take them, but it's amazing how frequently drugs users forget that the drugs alter their perceptions of how the drug is impacting their lives.

I've fortunately only had a few of my friends succumb to addictions, but it was surreal to watch them remain convinced that the drugs (including alcohol) were actually helping their performance, relationships, and productivity while everyone around them could clearly see that the opposite was happening.

One of the most striking examples is benzodiazepine abuse. Benzos famously mislead users into a false sense of sobriety even when they may be so inebriated that they struggle to accomplish basic tasks.

Within the tech scene, I've also noticed this with LSD microdosing. The few people I know who (openly) tried it were convinced they were smarter and more productive while microdosing, but it was objectively clear to everyone else that they were thinking more slowly, generally more confused, making more mistakes, and so on. The difference is that the drug convinced them that everything they accomplished was a wonderful achievement that made them happy, which led them to perceptions that they were accomplishing more on those days.

I see similar trends in acquaintances with excessive marijuana habits: A general belief that the drug is helping them do more of the things they want to do, but they're clearly doing very little on the days they smoke. Obvious from the outside, hard to see from the inside when your perceptions are being bent to extremes.