Set your heart on something Definition 1 of 2Pro Tip 1/3Strong Desire Expresses a deep wish or ambition to have or achieve something. Once she set her heart on becoming a doctor, she studied tirelessly. Pro Tip 2/3No Casual Interest Shows commitment, not just a passing interest in something. He's set his heart on collecting every comic book in the series. Pro Tip 3/3Emotional Investment Implies strong emotional involvement in pursing a goal. They set their hearts on adopting a child and poured their feelings into the process.