How to find the right problem that is worth working on if I don’t have one?

I've been in a meeting with Michael Sibel (YC CEO) @mwseibel today, organized by the ITMO – University from St. Petersburg. It was a Q&A session, and I got a chance to ask him a question. I asked a simple question. How to find the right problem that is worth working on? He answered me something like: 1. Start working on any problem that seems worth working on for you. Ideally, on your problem. 2. If you don't have your problem, join someone who does. Just work on something you find interesting. 3. Accept the fact that you will constantly fail. There will be more failures than successes. 4. If you take those failures as learnings rather than failures, you'll eventually stumble upon the right problem worth working on and build the right solution. It's going to take years. 5. The fun and joyful days in a founder's job are rare. Mostly it's monotonous work and constant fails. Keep going.