"Good trip" and "bad trip" are older terms created by recreational drug users who wanted to get high and have a good time.
Today, in therapeutic contexts, they use "easy trip" and "difficult trip" to give patients a sense of what to expect, and some context for how to interpret the experience they're about to have.
Some trips are like tropical vacations; peaceful respites. But others feel closer to climbing a perilous mountain, or trekking through endless desert, or slogging through dark marshlands.
Some of the most fulfilling journeys in life can be quite uncomfortable and hard, and notably, 70% of people that have bad/difficult trips do not regret the experience.
What makes the trip is worthwhile is if it causes you to learn and grow in a meaningful way.
I have had good trips and bad trips on a variety of highly psychedelic substances, and I've had a lot of those trips. Trying to engineer the trip out of the drug to get a desired psychoactive result free from pesky side effects like not being as grounded to reality for a while is absolutely missing the forest for the trees. Not to say that it can't produce some benefit but it's leaving a lot of unexplored potential on the table, largely in deference to failed puritanical ideals about recreational drug use.
I’ve had several bad trips in my life. I think they are the most impactful and clarifying. Uncomfortable for sure. Good trips let me know I’m comfortable with myself. Bad trips usually lead to uncovering or bringing to the front things that need to be addressed in my life.
It's not that simple at all. Bad trips can be more therapeutic than good ones. If you have tripless neuroplasticity, (a possibility I doubt) then what's your feedback mechanism? You might wind up selecting for shitty or dysfunctional behavior.
I've had many bad trips throughout my life, and they have always been the most educational. Learning about your shortcomings and confronting your demons and traumas isn't supposed to be a pleasant experience.
If you had a bad trip, you might feel differently about it.