I drank Crystal Light exclusively for about 3 years and the more I drank it the more I wanted. I drank about 10 glasses a day. When I saw a video about Aspartame including some of the symptoms of it (like severe joint pain) I quit cold turkey. My knees used to hurt so badly that when I stood up I couldn't walk right away. I had to stand for a few seconds before I could walk, and I was in my early 40's! My vision had also diminished significantly during those 3 years, etc.
I decided to quit all at once and I never thought I'd have immediate and disturbing and scary side effects from stopping. My hands and fingers felt like they were extremely swollen and I couldn't close them. I couldn't do normal things like grasp a zipper or even had problems picking up and changing my young kids. I had vertigo so badly that I could not get up and had to call my husband to come home from work. I had severe anxiety and nausea. I never ever go to the doctor, but during that first week off Aspartame I went to the doctor (I think they thought I was crazy) and the ER. These symptoms have never before or since ever happened to me. I was "coming off of" the chemical Aspartame and it was slamming my body.