Sundays to me remind me of sunny, relaxing days, no matter the season. A day for the rest of the world to rest, but my parents never got to rest on Sundays. Sundays were their busiest days at our family restaurant.
To me, an ideal Sunday would be just like any other day of rest: lots of time spent reading, catching up on everything else that I fell behind on during the week, and just relishing the time with my loved ones. Lazy Sunday, but also productive.