I used to think like that, but this is a moving point. As long you finish a list of things that you deemed important, many others will replace the old ones and the list actually will never be empty. This feeling of fulfillment will never come.
So I'm doing differently this time in my startup (that was also my side project for a while). I created a funnel and measured everything. I cannot develop anything on top of my head (We, developers, are creative by nature, and it's easy to find a myriad of interesting new features). The new feature needs to come from data and user feedback only. No exceptions.
The funnel is completed and has being measured, then the project is completed. Everything beyond that is just optimization. This was a shift in my mind and I feel much better because I finished the project, instead of constantly open. And of course, this is not a mind tricky. The project is actually completed.