I prefer odd numbers myself for the most part. I think it stems from an artistic thing. In pictures (for example), I don't ever want to have two chickens, four trees, or six whatevers. Makes things too symmetrical, and that's not what I want. Looks more artistic if things are unbalanced. So I've gotten into the 'odds' habit, and now I have to do things like put three or five ice cubes in my glass (that is, when I put ice in there...I usually go sans ice).