Hermann von Helmholtz

The older view of the nature of heat was that it is a substance, very fine and imponderable indeed, but indestructible, and unchangeable in quantity, which is an essential fundamental property of all matter.

What appeared to the earlier physicists to be the constant quantity of heat is nothing more than the whole motive power of the motion of heat, which remains constant so long as it is not transformed into other forms of work, or results afresh from them.

When I start getting embroiled in heated debates and feeling stressed, I just turn everything off and disconnect from the world. I simply tell my colleagues and friends that I am not well and need to cancel all meetings for a day or more. I take it easy - go for a long hike, take a vacation somewhere, or just stay at home and read.