The phrase "sunny disposition" refers to someone who has a naturally cheerful and positive attitude. They are usually happy, optimistic, and bring warmth and light to others like the sun does. Full definition
Obviously, a good night's sleep is crucial for a child's healthy growth, not to mention sunny disposition. (verywellfamily.com)
I'm hoping that carefree sunny disposition of yours doesn't suggest that you'll shrug off the looming failure of our company like the loss of an NFL pre-season football game. (businessinsider.com)
Fourth - grader Ida B's usually sunny disposition turns steely gray after her parents break their promise to home - school her. (booklistonline.com)