I have had direct experience with the effects of health on the quality of trips (and in general, everything else, too).
I suffer from a chronic illness primarily affecting the colon, though there are other symptoms as well. One of the treatments for active disease is oral prednisone, which has a slew of unpleasant systemic effects if taken for long enough or at high enough doses. ("Enough" appears to be relative -- my doctors were entirely unwilling to define it 8))
My "heavy phase" of tripping happened to coincide with the half-year or so immediately following my diagnosis, while I was experiencing the disease in its active state. My trips during this period, almost as a rule, lacked the "magic" that was present before I became ill. While I was on prednisone, my mental state deteriorated, and the anger precipitated by literally everything in the surrounding world leaked into my trips. I literally couldn't trip 75% of the time I took a psychedelic; I just felt "altered" in a sense, but without much of a mental shift, regardless of the dose.

On one trip in particular (150mg harmine HCl + 25mg 4-AcO-DMT), I experienced a series of ego-deaths, where the first "thought" upon "waking" and the last before "dying" each time were envenomed with anger.
As my health improved and I slowly tapered off of the prednisone (without a doctor's supervision because I didn't have health insurance and couldn't afford to see one - isn't America great? NB: prednisone withdrawals are not fun) my trips became more powerful and less unpleasant. I can now take a regular dose and trip, and my most recent trips have been among the best I have had.
I should add that as a consequence of my having the combination of little money and a digestive condition, I now prepare all of my meals from fresh foods and no longer consume processed foods. I decided while on a 4-aco-dmt trip to alter my diet in this way while I was still sick, and that decision has made all the difference.