Number 1 from Kevin Pang’s Top 10 things that annoy programmers is ‘Their own code, 6 months later’:

Ever look back at some of your old code and grimace in pain? How stupid you were! How could you, who know so much now, have written this?— Kevin Pang

This is so painfully true; except most of the time it doesn’t take 6 months for me to hate my own code, it’s more like three.