Personal central heating sounds so familiar for some reason.....can't think why
as an addition to Darkness's idea.
I let the flames I make burn outside of my aura Obsidian that way they don't make huge amounts of heat inside the body.
I don't know how much heat you make but you should be able to filter the heat out rather like a reverse psi feed.
Taking the heat from your central core and passing it over the outer edge of your Aura so that the movement there causes it to slip off into the atmosphere around you.
Please excuse me but I presume that your essence is reasonably big because I have noticed that part of the problem of fitting a larger essence into a small body is that it concentrates the heat your essence naturally makes into a smaller space. At normal size the heat is negligable but when compressed your essence makes more heat than your slightly overfilled body can dissipate naturally on it's own.
Zygo