What an amazing manga.
Each day you age you get further and further away from youth, fitness, stamina, and vigor.
Today is the day you are the youngest you will ever be.
If life by default ends with pain and degradation, then humor, health, knowledge, courage, action, and love become ever more precious. They are way more valuable and scarcer than we often think. So it is worth it to lean more and say yes to them - to what makes us feel more alive.