perception is reality, to a significant degree when it comes to tripping. This is why meditation is absolutely essential for the psychoactive journeys; I've had bad trips which just stayed bad because I was just "riding it out" and "hoping for the best" without enough confidence and experience in these matters.
I've also had bad trips before which I turned into good ones simply with putting everything into a more positive perspective. So it really does depend a lot on the state of mind that you're in, and your own conscious response.
I've said it before, and I'll say it again here because I think it's absolutely true and relevant; psychoactive substances just give you an expression of your own conscious state, amplified... so if your consciousness is negative going in, then the trip will be a bit shaky, but if you learn to meditate within the experience and just go with the flow, allow things to happen and unfold as they will, and just be completely conscious and aware in the experience as much as humanly possible, then you have a certain self-control of your mind and it's expressions within the trip (to what degree may vary on the amount of substance taken, the kind of substance taken, as well as personal response)
So, to a degree it does depend on you and your own mental state, to another degree set/setting and proper dosage can all play a huge part.
I also do believe that this same "perception is reality to a degree" statement also applies to all of life in general and how we choose to perceive the world. A more positive disposition can certainly lead to sunnier days in a lot of instances. And, in a lot of other instances, can make bearing the bad weather a much more peaceful and relaxing experience.
As the saying goes; In the end, everything will be allright, if it's not allright, then it's not the end