About 6 months ago, when I discovered Asperger's Syndrome. I'm only half-kidding.
I knew I didn't know many people like me, but I thought it was because most people were morons and that I was somehow intellectually superior to them. My mother has been telling me for decades that she thought there was something "wrong" with me, because I was so introverted and fearful of people and scared to talk on the phone; clumsy, highly intelligent but unproductive and seriously lacking in "common sense." And I kept saying "There's nothing wrong with me. I'm fine. Stop worrying", as I was rocking back and forth, tearing sheets of paper into little teeny pieces and zoning out every 10 minutes.
When I started reading about AS, I just went "Ohmigod!" I fit everything so perfectly, scored high for AS on every test, and behaviors I thought were common to everybody, suddenly became markers for AS. It explained things such as my anxiety and housekeeping problems and my lack of social skills. It even explained my unique walking style -- side of my feet on to my toes, and I take really small steps for as long of legs as I have. I've been trying to figure out for eons why I was picked on in school -- from 1st grade up until graduation. I guess I was more obviously an oddball and misfit than I ever realized. something those with an abusive personality seem to pick up on instinctively.