I have heard about an exercise that can help put your life in perspective: write your own obituary. I have not tried it, but I have thought about it, and sometimes bring it to mind when I am thinking about whether or not to do something. The idea is to think about how you want to be remembered. An obituary is a brief summation of your life, what you have done, and the lives you have touched. It sounds like a morbid thing to focus on, but it really isn't.
This is a chance to look at where you are in your life and compare it to where you would like to be. What really matters in your life? Are you focusing on your priorities, or do you spend most of your time/energy on things that don't really matter? What kind of person are you, and what kind of person do you want to be? With chronic illness and pain, you likely aren't living the life you expected. Pain and illness make your world smaller, but it doesn't have to disappear completely. I found good instructions for writing your own obituary on E-How. This person tells how to put a little humor into it, while taking it seriously as a way to keep you on track in the future.
It is too easy to feel sorry for ourselves, and to get ourselves stuck. Be realistic about what you can and can't do, but don't sell yourself short. Doing things you want to be remembered for may be more difficult, but that does not mean they are impossible. The writer of the instructions suggests this as a way to motivate you and jump start your life. As the saying goes, where there is a will there is a way. (Pun intended.)
After you write your obituary, pick one goal, and write out the specific steps it will take to get you there. The more specific you are, the more likely you are to work on those steps and reach your goal. Reward yourself, be proud of your accomplishments, no matter how small they may seem.