The power of the Government is limited in that Government cannot do everything it desires. This is so because it was elected by people, and assuming that the politicians in the goverment will want to be re-elected, they have to do what the people want, and not whatever they want: they have limits on their actions.
If the government was elected, they know they won't always be in power: they need to be re-elected. In order to be re-elected, they have to do their work well and not abuse the power: this limits the power of government.