First of the fourth month

As of today, I have not been on my blog this year. I agree with Ryan that forced blogging is not good! However, this is not forced.
I have recently become aware of concepts, principles, systems, etc. that come in fours. People who write books seem to think in fours and I wonder how pervasive fours are. There are four seasons - four quarters on the calendar. Four quarters in some sporting events and four leaf clovers bring good luck! There are four personality types in Myers-Briggs as well as four styles in DISC assessment. I could go on but you get the idea.
Help me think of things that come in fours and send them to me. As I find them, I am going to document them and save them just to see how many FOURs are out there.
Leave a comment of fours you know.