I'm curious to see how people would respond to this question now.
I disagree with the concensus, actually. I think it makes more sense that the amount of power you have changes throughout the course of your life. Mastery, or at least part of it, is learning to be more in tune with the force. Which allows you to harness more power.
I know there's no right answer, because different authors have different ideas, but this could be a great thread to post examples.
Raw Power:
--Grows--
[list]
[*]Galen Marek was already mentioned as an example
[*]Vitiate "shedding limitations"
[*]Luke
[*]Darth Krayt
[/list]
--Stays the same--
[list]
[*]Anakin as a child was said to be like fire. He had trouble meditating and was already incredibly powerful. Training only let him direct and aim his power better.
[*]Midichlorians are determined at birth.
[/list]
Mastery:
--Using power more intelligently--
[list]
[*]Sidious was said to use his blade in ways other people overlooked.
[*]Mace Windu unscrewed the droids on Dantooine, younger jedi don't.
[*]Anakin lost to Dooku in Ep II because he rushed into the fight.
[/list]
--More "One-ness"--
[list]
[*]Obi-Wan said that the force controls your actions, so getting "control" over the force wouldn't make much sense.
[*]Darth Malgus fought in such a way that he described it as watching himself fight
[/list]
Knowledge:
--Makes you stronger--
[list]
[*]In "Weapon of a Jedi," Luke tried to pull a lever down to open a door with the force for a number of hours, but couldn't. He managed only to do it when he let the Force tell him what to do, rather than trying to reach out and pull the lever.
[/list]
--Helps you understand/interpret the force better--
[list]
[*]In Vision of the Future, the Aing Tii were said to believe in a "Spectrum of the force" rather than the light and the dark side.
[*]Jocasta Nu, while being incredibly knowledgable, was not very powerful
[/list]
--Knowing more abilities--
[list]
[*]Sidious was said to be able to create abilities on a whim
[/list]