(Caveat: this clearly only applies to things that you do for fun. You should be very careful if you decide to stop caring about your audience at your day job.)
When I was younger, I got a lot more things done.
I would get an idea, and if it was possible for me to act on it, I would do that pretty much immediately; if it wasn't, I would just forget about it. Now-a-days, I write every "good" idea down, even if it seems like it would never be possible for me to do anything about it.
I would build the thing or talk to the person or study the thing. I'd use my basic, still-growing checks for whether or not that idea was going to actually benefit the world, but I'd only not do a thing if it was obviously a bad idea.
Now, I have a lot less time. So I take every idea, I meticulously catalog it, and then it's nearly impossible for me to do it.
How does this new idea relate to old ideas I've had? Can this new idea make any money? Is this new idea more important than the other things I'm thinking about working on? Will people even like this new idea?
It's that last one that's a killer. It gives me the excuse to say "eh, you know, maybe it's not even worth it." Some of the coolest things I've built have been seen and enjoyed by only one or two people, and I think that's totally fine.
"Would anyone actually use this?" is creative poison. "Will anyone actually pay for this?" is the fastest way for me to utterly decimate my desire to work on something for fun.