Pacing is a way of managing your mental and physical activites so that you do as much as possible without getting to the point where your M.E. gets dramatically worse. It is different from a graded exercise programme (GET) where you are encouraged to increase your activites gradually whether you feel better or not. With pacing you never push through the pain.
Many people with M.E. find that pacing works for them, but only a limited number feel that GET helps.
There are lots articles about pacing. Here are a couple that I find useful.
The M.E. Awareness New Zealand leaflet here
The Action for M.E. leaflet here