Just wanted to add another view on this: wasting a few days creating a perfect design for something that you never even create is not necessarily wasted time. During that time you're thinking through all the different interactions your product could have and getting experience on putting together a good design for when you do need one. It's pretty good training and you learn the same whether you wasted the time or not. It's obviously better to not waste the time, but don't knock yourself short for having done it after the fact since you probably learned a lot of important stuff that will help in the future.