Is it normal to feel mentally clumsy even though I'm smart?

Absolutely. ADHD affects executive functioning, not intelligence. You can understand complex ideas and still struggle with recall, organization, or verbal fluency in real time. That gap can feel deeply frustrating. Mental clumsiness often shows up under pressure or fatigue, when working memory is taxed. This can create the false impression that you are less capable than you actually are. Feeling mentally awkward does not cancel out your competence. It reflects how your brain processes information under load.