Remember the good old days when you were young? When someone lit the fires in your home so you didn’t have to? When someone polished your shoes? When someone paid the bills and cared for you? The speaker in “Those Winter Sundays” is remembering those good old days, though they didn’t seem so good at the time. But that's only because he was young and ignorant. Once he's grown up a bit, and has a few years behind him, he's able to recognize his father's love.
“Those Winter Sundays” suggests that no children can comprehend their parents’ love for them. They're too busy being resentful.
“Those Winter Sundays” suggests that becoming an adult means understanding your parents’ motivations and experiences.