I have a non-visible disability.  The pain I live with, sometimes severe, means there are some daily things I can’t do, or at least if I did them would make my pain situation worse.  However if you met me at the railway station, or anywhere else, then you would have no way of knowing that I have any physical difficulty at all!  Pain is completely invisible, and just like emotions I am sure it is felt differently from one person to the next.  Pain is also difficult to describe. 

Living with pain is a very emotional experience.  It is difficult and affects everything about you as a person.  Practically you may be finding things difficult too.  You may have lost some independence.  Living with a person with pain must also be difficult.  How can you possibly fully comprehend what is happening with them?  I think pain can act as a barrier between people, but it is a barrier that can be easily broken down with communication.  If you can help others understand how your condition affects you, including why it is you can do something one day but not the next, then they will be much better placed to help and support you both emotionally and practically.