Ah... the eternal question. Let me know if anyone has a definitive answer.
In my eyes though, it's to feel. So many emotions and experiences to make you feel different ways. It blows me away and makes me happy even when I'm at my most sad. There are so many wonderful things that happen. Endless places to explore. It's all about learning.
Of course, the answer to this question would also depend on your religious views (whether you have any or not).