You should not be concerned if you feel you did not do your best – there is no such thing as “best” for this type of assessment. The tasks are designed to be challenging and to measure your abilities by getting increasingly difficult as you answer questions correctly. Please be aware that this is only a snapshot of your cognition at the moment you are completing the assessment and that cognitive performance tends to fluctuate naturally from day to day depending on many factors (like your sleep quality, stress level, nutrition, exercise regimens, etc.).