So from my understanding, you need to demonstrate that to the character who is reflecting this affirmation, they accept both the pains and pleasures of life because both experiences are equally valuable. This is manifest in the often told story of the child who is putting sea stars back into the ocean. When it's pointed out to the child by an adult that there are so many sea stars on the beach that washed up for the recent storm and that the boy's efforts won't matter because most of the sea stars will die, the boy responds by picking up a sea star and flinging it back into the ocean. He then tells the adult, "It mattered to that one."
Probably the best summation of the idea comes from the titular character of the Television Show Angel. After getting a pretty harsh lesson that in the grand macro-scheme of things, Angel's missions and existence aren't much of anything, Angel comes to to the epiphany: "If nothing we do matters, then all that matters is everything we do." If nothing we do is important, than the most important thing in life are the actions we take and what we do with our lives.
Possibly one story that takes this and runs is "Forrest Gump" who's titular character seems to stumble through the back half of the 20th century. His life story is woven into that of great people, events, and innovations throughout the century, yet Gump seems to undersell what many people would think is a signficant event in his life. For example, Forest Gump has personally been honored by Presidents Kennedy, Johnson, and Nixon, all of whom had a major influence in their time... but Forest doesn't seem to care much about it. By the time he meets Nixon, Gump narrates it as if it's a chore to meet the President ("So I got to go to the White House, AGAIN. And I met the President, AGAIN). Where he shows the most emotional investment in his stories are when they involve people he cares about... As a narrator, he's at his happiest when he narrates about meeting Jenny and at his most despairing upon losing people he cares about (Bubba, His Mother, Jenny) and seems to register emotionally with people are lost to their loved ones (like he doesn't really make a connection with Kennedy, but he's emotionally upset by the fact that someone wanted to kill not only him, but his little brother. Similarly, he meets John Lennon of the Beatles, he doesn't even know why the guy was famous and refers to him as "some man from England" but does have some emotional weight when reflecting on Lennon's murder and the effect it had on Lennon's son.).
Gump's has personal and shared tragedies in the world and frame where the world is throughout the story, but he rarely mentions what he was doing during the death of the famous people he met... though other tragedies are reflected in television (Nixon gives his farewell address in the background as is the attempt on President Regan's life). Meanwhile, he never has a moment of enjoyment in major milestones ignoring such things as the Moon Landing and thinking about Jenny while the rest of New York rings in the New Year. The moments where he is happy are entirely personal to him and have little effect on the narrative beyond Forest's own personal story. The entire narrative, is in effect, from the point of view of a man facing another tragedy, but remembering that life still has plenty of moments that will make him happy. Particularly touching was in the finale, Jenny asks him about all the amazing sights he's seen and he reflects on the beauty of the world and the places and things he got to experience. Jenny laments that she wished she could have been there with him, but Forest tells her in all of those moments, she was always there for him... from the worst nights during his tour of duty in Vietnam, to moments he was working through emotional woes, to the times where his life was at peace. In each joy and each tragedy of his life, Forest thinks Jenny in those moments.