Early Game, Mid Game, and End Game... What's the goal of each?

[Spacepain]

What constitues and what you should do during each phase of the game, beginning, middle, and late, is one topic that the goal for most if not all nations is probably similiar.

As of present I understand that early game is a giant land grab, mid game is collection of magical resources, and gradual build up of small advantages, and the end game is when you let loose all the stored up magical goodness.

Am I wrong in this methology? It could easily explain why I am being beaten even by the easy AI....