On the days that my ill health gets the best of me, I imagine a place of serenity and do my best to picture myself there. This type of visualization is helpful in controlling the chronic pain I suffer with. Also, one of the best sites on the net for those with chronic illness is: 'But You Don't Look Sick' The site has many great articles and one in particular that I love called "The Spoon Theory." It is useful to explain to others how difficult life with a chronic illness can be. It is written by the site owner Christine Miserandino, and is very well done.
If you have a chronic illness and/or chronic pain picture your idea of paradise and try creative visualization.