Chronic pain can be limiting. Rather than learning to focus on what they can still do, some people regularly tell themselves that they "should" do tasks that are problems for them. For example "I should work in the garden, because the weeds are growing" or "I should really dust all those shelves" or "I should go to that function". People stuck in the "shoulds" continually make mental lists of what activities they ought to accomplish rather than making a reasonable list of activities that they really want to do.
(Warning: This entry is part of Negativity Week!)