Ask HN: How to focus if attention in a programming project lasts for one day?

When I start to implement a new Idea or work with something interesting new, I am working intensively for round about 1 day. Then I get distracted or disappointed and start something new. Over the years I become good at programming, because working with thousands of different things. But this comes also with depression and similar bad feelings. How to focus in the future and how to escape this cycle?