Energy

Is energy real or imaginary?  I have been having a lot of low energy days lately, but I'm beginning to believe that it's not a genuine energy crisis from which I suffer.  Perhaps it is a physical response to stress.  It's a pretty commonly understood thing that the state of mind can most definitely affect the state of the body.  From this general statement, I draw the conclusion that if low energy may be attained by reaching the necessary stress levels, conversely, high energy may be enjoyed when one reaches a positive mental state.  In this case, is the energy itself a viable thing?  Or does the energy exist merely as the physical manifestation of the mental condition?  At what point do physiology, psychology, and biology meet? 

Where does "E equals MC squared" come in?  Do I want to know?  Would I understand were it explained to me?  .......Then why am I asking?  That's one of the great things about me.  I am perfectly content to ask questions without receiving answers.  Yes, there are times one requires answers:  Are you okay, having fallen down a flight of concrete steps?  Is that buzz haircut going to work for you, Mrs. Nesbitt?  Would you prefer chicken or fish?  ........there are for me, however, many ponderables that are lovely and interesting without mates.  Not every woman needs or wants a man.  Not every rose has a thorn.  Not every question requires an answer.