The song "Happy" by Plain White T's is about the desire for happiness and the longing to escape negative emotions. The lyrics express a dissatisfaction with feeling bad and a yearning to feel good. The protagonist wants to make the most of each day without wasting it and seeks to have fun without resorting to harmful behaviors like getting wasted. The song suggests that happiness is found in simple pleasures and enjoying the thrill of life's experiences. The mention of rain falling and friends calling implies a positive atmosphere and supportive relationships. The protagonist also mentions the need for sunshine on their face and moonlight on their pillowcase, indicating a desire for positivity and romantic connections. Overall, the song conveys the message that embracing happiness and avoiding sadness is the ultimate goal.