More words of wisdom from Beust:

What will keep preventing dynamically typed languages from displacing statically typed ones in large scale software is not performance, it's the simple fact that it's impossible to make sense of a giant ball of typeless source files, which causes automatic refactorings to be unreliable, hence hardly applicable, which in turn makes developers scared of refactoring. And it's all downhill from there. Hello bit rot.

I hate giving anecdotal evidence to support my points, but that won't stop me from telling a short story that happened to me just two weeks ago: I found myself in this very predicament when trying to improve a Ruby program that 1) I just wrote a few days before and 2) is 200 lines long. I was staring at an object, trying to remember what it does, failing, searching manually in emacs where it was declared, found it as a "Hash", and then realized I still had no idea what the darn thing is. You see my point..

To be brutal, if you put down a tiny program for two days, come back to it, and can't make sense of it? Please, please, stop writing code. To be brutal about it, you simply don't have what it takes.