Challenges are the key in life. You always have to challenge yourself and try to get to different states.
Satisfying yourself requires challenges because when you come to a certain point, you're not happy anymore. You don't feel happy with the way you played one year ago, you have to always make progress. So that's a challenge.
My biggest musical dream is to keep playing all my life. There's nothing bigger than that and that's very challenging because you have to satisfy yourself at every stage.