Do you keep track?

I was just wondering is anyone kept track of their projects/clients/money made etc?

I personally started today as I am redoing my IT coursework (database) and decided to make 1 for my projects and clients. It tells me average earnings, most earnt, least earnt etc.

I know it will come in handy comparing the amount of money I've made to what I could earn with a normal Saturday job, so how about you?