一纸清欢一念长欢
[yī zhĭ qīng huān yī niàn zhăng huān]
Translated as 'a note for joy and a thought for eternal happiness', it seems to imply contentment found even in the simplest form (like paper) and wish that such simple joy can be sustained forever. Perhaps there's an appreciation for minimalism and modest happiness in daily routine or life moments.