Cactus to me has always been gentle and kind, but serious. It seems to lack the goofy hilarity that accompanies mushrooms, but has the balance of LSD.
It's really it's own thing and must be experienced. As you know, words seldom do these types of things any justice.
All of the psychedelics I have done have many things in common, but each one has its own spirit and flavor and yet they are all cut of the same cloth. Similarly, there is a noticeable difference between just mushroom species!
In my experience, I don't think I could fathom a bad time with cactus, but that's not to say it's impossible. The worst I've gotten is an under dose!
Be an adult only when necessary.