However, things have changed a lot. Nowadays we're bombarded with ideas and incredible "opportunities" of stuff we can make. It's almost like ideas are shoved into people's heads.
So, I have to add to Mr. Feynman's words an update:
_Be sure that the thing you want to solve is really the thing YOU want to solve_
This is specially true for software development and closed platforms. Sometimes, software vendors have this way of making developers work for free for things they won't get back, ever. They'll do conferences, and attract people, and show you all those nice tools you can use to solve problems (as long as you use their paid platform).
Don't fall for that shit. Remember Twitter and Reddit closing their APIs, platforms being discontinued, companies cannibalizing successful apps by independent developers. Those people wanted to solve problems, and they got scammed.