Things like not being able to watch a movie, or even play some video games without missing huge parts of the story, or sitting through a conversation with a group of friends trying to constantly "catch up" to a topic that I missed a few minutes ago, or trying to be self aware enough to not change the subject on people too quickly because my mind has already changed topics twice during their conversation.
I love reading, and it's almost 100% out of the question when I'm not taking my medication. Somewhere around the 5th time of re-reading a paragraph trying to remember where I trailed off only to realize that I just did it again makes it really not a great experience.
Even the worst case scenario of the medication severely increasing my chance of heart attack, stroke, or Parkinson's wouldn't make me stop taking it, because it's given me a life. And I would rather live a shorter happier more fulfilling life than a potentially longer one.