I've had days where I felt more forgetful and clumsy than usual. When that happens, I stop trying to multitask, write down what I need to do, and focus on one task at a time. Taking short breaks and getting enough sleep also helps me think more clearly.
Mental overload can make people feel forgetful, distracted, or mentally slower. When that happens, I think it helps to simplify the day, write tasks down, focus on one thing at a time, and take short breaks. Reducing mental clutter helps you to think clearly.