yep. I look back at some bits of my own code and realise they are a mess. If it needs changed anyway, and I have time, I'll use the "fresh look" at my code to decide what is wrong with it, and what could be better. Refactor from there.

Another one would be constantly changing requirements. So you start with something nice. Add a quick hack to do a little more. Rinse, repeat, until it becomes an unmaintainable mess.

That was in the MVP (minimum viable product) section. I also referred to an old post of mine, on bad code http://www.mehdi-khalili.com/bad-code, where I explain that in great details. I hope you find that useful.