Abby, Well, there is a science behind emotions and neurotransmitters! This is simply a sampling of the info out there - it's endless.
Doctors, especially neurologists, often pooh-pooh emotions, as if emotions are a "lesser" form of being. There's a great book called "Molecules of Emotions" by Candace B. Pert, PhD that I have which is a fantastic view of the "neuroendocrine" system and how emotions affect disease.
These are more "scientific."
http://www.loc.gov/loc/brain/emotion/Damasio.html
http://www.psychologistworld.com/stress/fightflight.php
http://www.fi.edu/learn/brain/proteins.html
Not a great source, since it's "Yahoo Q & A," but interesting.
http://answers.yahoo.com/question/in...0092543AASuyTZ
So it's not silly to think emotions can make you weak. It's a complex series of chemical reactions in the body which includes acetylcholine.
Have you ever stopped for a minute to check if you're tensing your muscles? It's amazing how often I do that. So I try to relax my entire body whenever I have a chance or if I'm stressed. It really helps.
Annie