(if you can't change any of your decisions, you have no power)

Change presumes comparison to something else. You determine your decisions, but there doesn't need to be anything that can be compared to them, so there doesn't need to be any "change". (I understand that you are talking in the context of "status quo", so this is more of a foundational nitpick.) In determining your decisions, what matters are the reasons/causes of these decisions. If decisions are such that they optimize your values, that gives them "power" of enacting these values. Someone else's decisions can also have the "power" to optimize your values, which is when "trade" is useful.