Whenever my seemingly perfect solutions break down, it’s because I didn’t imagine the edge cases I’d eventually have to handle.

It’s OK. We can’t predict the future. But when you notice it happening, stop digging. Don’t just apply patch after patch after patch. Instead, unwind your original solution and extract a better one.

http://www.justinweiss.com/blog/2015/01/13/when-edge-cases-poke-holes-in-your-perfect-solution/