Final answer:
The person suffering from this belief is experiencing Illusory Superiority, a cognitive bias where individuals overestimate their own abilities and believe they are superior to others.
Step-by-step explanation:
The person who is convinced that they are gaining admission to Harvard by merely applying is suffering from Illusory Superiority. This refers to the cognitive bias in which individuals overestimate their own abilities and believe they are superior to others. In this case, the person has an inflated sense of their qualifications and believes that they will be admitted to Harvard without considering the competitive nature of the admissions process.