None of the names or terms I'm using for worldbuilding are final so please don't judge me too hard on them. Sorry in advance if the answer seems obvious or if I formatted the question incorrectly, I'm not the sharpest tool in the shed.
The Big Bang occurred and the stars started to form and go supernova spreading the elements that were within them far and wide throughout space. The solar system, including the Earth and the life upon planet Earth, is thought to be made of this star dust. In my world an additional element was formed that ordinarily can't be observed by humans, Metatron. It's a type of metal whose atoms are present in every living thing like how carbon is. The special characteristic of Metatron is that it reacts to and is manipulated by the thoughts of sentient creatures. When this happens the thoughts and the Metatron merge to form a new substance called Phantasm, which can then be used as fuel for supernatural powers.
Powers like conjuring or manipulating the elements, illusions, non sentient creatures and more. Humans constantly give off a small amount of phantasm due to their emotions interacting either with the Metatron atoms inside them, or with the particles of Metatron around them coming down from space. Eventually these pools of Phantasm can be further manipulated by collective human thought into creatures called phenomemon, which the heroes of my story fight.
The trouble I'm having is establishing limits so that the characters can't do everything, as well as having those limits make sense. Ideally I'd like it to be a matter of using up the resource that is Phantasm. This would lead to a kind of exhaustion that characters would have to recover from before using their powers again. So either consuming or causing the components of Phantasm unusable for a time. Since you can't really run out of thoughts or render them them unusable in my system, that leaves Metatron. While burning up the Metatron particles or objects around them makes sense, I don't know what to do about the Metatron atoms inside my characters. Which brings me to my question, since atoms can't be destroyed how else do I make the Metatron atoms in my characters unusable or inaccessible for a period of time?