There is a lot of things stress can do to your body some people can be so stressed that they won't sleep at all which can be bad for your body you need to rest your body so it can relax but if you are stress about something (there are number of things that can make you stress) you won't be able to sleep and it will make your body really tensed thats where you get your muscles ache and head aches and you just feel very weak. So thats what I think.
