Ask HN: How to maintain interest in completing a Sideproject?

Well, I have a big problem when it comes to completing things. Every time i have an awesome idea i start working on it asap and stay focused on 120% like a beast for some good time.

And always when it comes to finishing the project i loose interest. For a example, I do have a big thing i want to create. I have a complete concept since this idea exists for about three to four years now. We've got a professional logo designed which is the best one I've ever let a contractor create and every aspect of the project is perfectly planned. I already had some type of prototype but always when it comes to "finishing" it, I'll just loose the interest in completing it. Everytime I tell someone about the Idea everyone is just amazed and says it's perfect and that I really need to finish it. Now im a freelancer and don't have much time for side-projects anymore because im struggling to make enough money to survive. I often thought about maybe trying to get some funding but in germany i have no idea how to get that done.

So to get back to my main question: How do you maintain keeping intereset in finishing your side projects?