Most of the psychedelics i do these days i weigh up myself on a milligram scale, so underdosing is something that only happens when taking an unfamiliar batch of LSD. I find that I can tell if it's good acid pretty soon after ingesting it.... while weak acid will continue to feel like a first alert of taking a substance for an extended period of time, and if more is available, i will certainly eat it.
For myself, i quite enjoy all-immersing mind-blowing psychedelic experiences, and i'm pretty comfortable with tripping and being able to deal with whatever comes up, so if i get hit harder than i was expecting, well, that's kinda what i shoot for! i'm not at all into taking benzos to abort a trip, but i will drink some mugwart & passionflower tea if i'm looking to get my body to relax toward the end. Especially with 2C-E, that stuff has some lingering body-tension for sure.