Labelling people as either good or evil, with no shades of grey?

I did this yesterday towards one of my nurses, refused to take the medication she gave me because I felt scared that she may have poisoned it somehow. Another nurse had to give me the medication. I was feeling extremely anxious throughout the whole evening and night. I was able to talk to other people just fine, but I couldn't towards that one nurse because of the evil label I had given her.

Even now I am feeling confusion...is she good or evil? My psychologist is trying to get me to stop thinking in black & white terms, and go to shades of grey...but it is difficult sometimes when my mind tells me otherwise.

Does anybody else struggle with this?