Great insight on founders needing to think more like investors. Something that may help in thinking this way is: If you had $100,000 to invest in an idea (and would not be personally involved beyond that), would you do it, or is there another idea with a better risk / reward profile? Use that as your emotional anchor while you factor in your excitement for the idea.

You're right about traction - it can get you excited even if you're in a mudane industry. That's much better than doing something "cool" that never gets off the ground.