Also, to add one more tip about the pacing of inhalations: I always feel tense for hours sometimes before an experience, and it is only relieved once that hit is in my lungs. Once it is, I have this mindset like, "ok, we're on our way. There's no sense in trying to turn back now. A very real physiological reaction I have is that the first hit in particular can be a bit harsh, but I find that once it is in my lungs for a few seconds, my lungs, shoulders and just whole body relax, and I can hold in the hit as if holding a normal breath without the harshness or anxiety. The second hit usually goes down easier.