In therapy they use set, setting, and an assistant to keep you on a less challenging trajectory!

Still, some people have a lot of hard things to work through so the trip may be more enjoyable for some than others.

My impression is that if you learn something positive from the experience, a good trip and a bad trip lead to the same benefit. I think you experienced how a "bad trip" can still be a good experience.

Maybe it's like catharsis? At least for people who weren't aware of the fears and anxieties constantly in their head, it can help lift the veil on how their mind works.

Some people don't seem to find anything meaningful during the trip and likewise they don't seem to benefit. They just get the bad trip with no obvious benefit.

It seems to me that the adage "set and setting" holds true - if you go into a trip with a positive mindset and setting, you're much more likely to have a positive experience. I've also heard to go into it with an intention - that might help make the trip feel more meaningful, which can make even challenging trips rewarding.