I used to get horrible come-up anxiety, for years, when I started tripping. I believe it is because it is such a profound change between normal consciousness and psychedelic consciousness. The body feelings are strange, and the mind is put very off-balance, so it causes you to become very anxious until you get used to it and the transition is complete. On almost all of my early trips, I went through a period of regretting taking the drug, with intense anxiety and unpleasantness. I always had to repeat mantras to myself, things like "you just took a drug, this will pass". because it's true, and it will. I always found that if you just hold out and do not succumb to the anxiety, it always passes once you reach the peak. I always thought of it as psychedelics giving me the hangover up front, instead of the hangover afterwards.
Also, your set and setting have a huge part to play in the come-up anxiety. If you're stressed out or not feeling great, it will be worse. But even moreso, in my experience, if you are uncomfortable with your surroundings, it will be far worse than if you are comfortable. I have also found that if I am doing something physical with my body, the come-up is much easier and more enjoyable. A good example is if I am hiking, or exercising, or even just walking around in circles. being outside also helps a lot, I always feel much more comfortable on psychedelics when I am outside compared to when I am inside.
I have been tripping for 21 years now, and I am happy to report that it has been a long time since I experienced significant come-up anxiety, or bodyload. Nowadays, and for a long time, I find every stage of almost every trip to be pleasant and easygoing, except sometimes if I take very high doses, it can still be quite difficult at times. I don't even get bodyloads anymore, or nausea. I think the more experience you have, the more easy it is to transition from sober to tripping. I think the bodyload is largely psychosomatic, your body's response to the anxiety.
