While working on a task, going well with expected outcomes, creates a sense of confidence that we could do anything. After the lunch, you attempt the task and it didn't work - we feel like total disaster.
Mood swing causes the evaluation to be corrupted. Our reasoning ability is not constant. It changes with time of the day, work pressure, motivation.
Our brains inability to do computation and holding information at the same time. For example, you could answer 2 x 2 = ? but - 22 x 22 = ? (take significantly longer), we know how to compute but we need to hold the intermediate results.
Keeping a flux benchmark, which is not clear to make decisions upon.