In my experience, the shutout/subpar experiences occurs when one is either "abusing" DMT, is not following its guidance, has developed mental blocks or are living an unhealthy life. Or a combination of all these factors.
When i first delved into the world of DMT, i was a vegetarian for 6-7 years. I wasn't super into health and nutrition, but did a fair amount of bodyweight exercises to prevent sloth and whatnot. I wasn't trying to get big or strong. I was trying to maintain my health rather than improve it. At that time, my trips were otherworldly and simply divine. Every single trip. Over a hundred or so trips, each with the immensely exquisite breakthroughs that DMT is known for. Then i moved my living location after starting a new job, and i resumed eating meat. I ate a lot of fast food out of convenience. I hardly exercised, and generally wasted a lot of time. I smoked a lot of ganja (which isn't that different before the move, to be honest). In fact, one particular trip advised me that i should smoke less. Ganja was at times an irresponsible but well meaning friend. My trips with DMT at that time were relatively lackluster, but would still be very intense to a newbie. I would get the occasional revelatory breakthrough. However, i am not a newbie, and was sort of disappointed by the lack of intensity that i was accustomed to.
I have recently resigned from that position, and have started taking my health more seriously. I'm now exercising harder than i ever have, with the intention of getting much stronger. I have not had DMT in a while, and won't for a few months due to living conditions. So in the next few months, i will be drastically changing my health and lifestyle, so lets see if my breakthroughs become what they used to be. If anything changes, i will post a detailed thread about the effects of lifestyle on the DMT experience.