This post sort of follows on from Kooky's post, we must both have been on a similar wavelength today.
People with CFS have to deal with all kinds of emotions in relation to dealing with chronic illness, theirs and their partners/families lives can be turned totally upside down, which in turn puts immense strain on relationships and mental well being.
Add to this the fact that some degree of emotional lability is not uncommon in CFS and what would normal be small things can upset someone with CFS greatly or make them angry. I think the main base of this is frustration and grief for your former life. Frustrations that you cannot do what you did before and anger as you want to be able to do things. Grief is a strange emotion not just appearing when you lose someone, I find I almost mourn for my old lifestyle, the old Carrie.