Nothing. Purpose implies the potential for failure and while there are certainly circumstances that I would consider personal failures, there are none so great that they would invalidate my existence.
That said, I have a vision for my life and the state of the world that I would like to see realized. I want to see a world where climate change is taken seriously and recognized as the imminent threat that it is. It will be waiting on the other side of every economic crisis or war that man chooses to wage.