HEat & energy
What is the major difference between a live body and a dead one? All the same parts are there. All the same hormonal chemicals and bodily fluids are present at least up until mortification. However, there is no heat and there is no energy! The missing factor is the life force that animates the living body.
Heat is the catalyst that promotes the transition of life/energy from a neutral to an active state of being. It moves energy; stimulates circulation and promotes metabolic functioning - which dictates how efficiently your body stores and utilizes that energy. In order for the body to operate efficiently there must be an adequate source of heat to promote a consistent and uniterrupted flow of energy. Lets take a look at our cold blooded - reptilian friends for example. Cold-blooded animals get their heat from the outside environment so when it is cooler their metabolism slows down; and their entire energy output level is reduced in accordance to the amount of heat sustained within their immediate environment.
Now in comparison, as warm-blooded land dwelling mammals, our first and primary source of energy is the oxygen that we take in at every breath. The oxygen fuels our blood cells and stimulates circulation and the second source of energy is the food/nutrients/physical sustenance that we ingest via mouth. When properly digested the food/nutrients energizes and/or influences the functioning of our cells, providing information for them to behave in a manner that either promotes or degrades our well-being.
Let us keep in mind that metaphorically and esoterically speaking, heat & energy also pertain to the passion one has for living; one's zest or zeal for life. Often I've heard people speak about their ambitions and inspirations with relation to a source of heat. For instance, lets look at a few statements regarding influence, movement, and heat that highlight the link between being passionate and making progress. When others want to know what motivates you, they may ask, "What fuels your fire?" Or when an individual has reached a peak in performance, they'll say "He's/She's on fire!" These are all statements that speak to the fundamental nature of elemental science - acknowledging that temperature influences energy.
Take some time to consider what is fanning your fire at this moment? Is your source of heat and energy sustainable or short fused? Is it reciprocating or debilitating? Can it be recycled and reused or does it have to be replaced due to overuse/burnout?