When creating something you see every flaw, rather than every thing it does right. If you're too heavy a critic of your own work, it can consume you and give you a very bleak outlook... there needs to be a balance point where you look past it's flaws and see it for the final product it is and how people receive it. Oft times, most people never see those flaws you do and you end up learning that they mean so little in the big picture of things. It's a weird dynamic. But many artists go down the same road every time they craft something.