[jastr]

Lots of developers believe that if they think hard enough and choose the right side project, it will succeed.

I think the takeaway here is that chance plays a big role. So increase your chances by shippings lots of projects. And a tip to ship several projects is to stay emotionally, physically, and financially healthy.

[sam0x17]

Well it also depends on what your success criteria are. If it's a side project and you've invested nothing in it other than your own free time, success could be $200/month in eventually passive revenue.

[HeyLaughingBoy]

Success also depends a lot on your approach. If you define it as $200/month revenue, then you're probably better off building something you know other people want. If success is "I built this really cool thing" then you can build something only you want.