It's hard to generalize. I think the amount of perfection I demand in a solution is proportional to some combination of its importance and my interest in it. I have no trouble putting in place simple, hacky solutions with the intent of changing them later, and then actually changing them later.

My side projects, in particular, are where I allow myself to roam freely, and I often end up prioritizing unimportant (but interesting) work that is only tangential to the core idea. When I am only accountable to myself, then it becomes too easy to get unfocused.

Perhaps the original question should be rephrased as "how do I keep myself focused when working on side projects, since I'm only accountable to myself."