I hate when people tell me to just "get over it" when they don't understand my random fears. My mom used to have pretty bad SA when she was younger but it's not as bad now and she always tells me to not let my feelings control me, to not let them run my life, but it's like damn! if I could, I would! Another good one is "people have to do things in life that they don't want to do" as if I just don't want to go to the grocery store or something, when in reality it's like, no, I don't want to go to the grocery store because it scares the crap out of me and I will probably have a panic attack...!
The worst things that people can ask or say are things that belittle SA, OCD, depression, etc even when they're trying to help.