In the movie, he gradually learned the importance of Life, Love and Time. In his case it was living positively, with great passion and imagination, free and serving others without reservation, friendly, focused, disciplined and most importantly, with a lot of love in his thoughts and in his heart.
Only then, he converted bad days into great moments, simply changing his perception of them and the way to face and change them. He sees them as opportunities to serve, to love and value everything, even in the most difficult moments.
And then all the boredom and resentment that accumulated in his repeated daily routine disappears to become a wonderful life, although the days remain the same.
We also see how death scares him at first and affects him intensely, but then he ends up accepting that reality, and this reminds him that time is <short>, but we turn it into <long>, living intensely and with love.
In conclusion, in this brief time that we call Life, we should not seek happiness. We should feel happy all the time, even when we are looking for it.
I don't know, it would be great if you would watch the movie and share your thoughts and conclusions, who knows what else we can find.