Psoriatic arthritis doesn't just affect your skin and joints. It can release chemicals in your brain that get in the way of how it works. You may feel tired, forgetful, and unable to think straight. In other words, you have "brain fog." The best thing to do is to plan for it: Write everything down, from dentist appointments to grocery lists. Use sticky notes, a day planner, a dry-erase board, or a memo app in your phone. Keep a log of when you feel sluggish, and plan around these times for when you need to be alert.