I have had several joint replacements, which can be quite disabling while healing, and now have CHF, which on a day when I am retaining fluid can make it hard to breath, so I have a handicapped hang-sign in my car but I never use it unless I really need it that day as I understand how it feels to need it and have them u available.
In fact I needed the handicap toilet the other day (i take strong diuretics for the CHF) and it was in use......and out pops a 19-ish year old girl...literally bouncing out. She will think twice next time I think......

My best friend has a bowel problem. It does not affect her much, nor would you notice anything by looking at her, except that she has to wear what is effectively a nappy, and sometimes she needs to change it quickly very quickly. The powers that be, are so unsympathetic to invisible illness, that they took away her Blue Disability badge, which helped her to park her car near to public toilets. Because they said she could walk fine and the badges are only for people with walking difficulties.

Yes this is wonderful. I have heard this before and it always resonates.