Efficient governments are concerned with providing the services their citizens have determined are valuable - whether health care or public security. They are constrained - efficiency - to do so at a reasonable cost in resources and in ways compatible with their citizens' rights and values, like fairness and privacy. That means they are constantly in conversation with and under scrutiny by the people, and the civil society institutions from religious institutions to courts to think tanks and the free press who represent them.
Effective governments are concerned with generating particular outcomes, like ending terrorism or drugs or 10% annual economic growth. They are assessed in terms of their ability to control the world and bring particular things about. As a result of this over-focus on often unrealistic particular goals they tend to neglect other goals, meaning that they fail to consider both the full opportunity cost of e.g. The War on Drugs (all those other social programmes that won't be funded) and the causal impact of their policies (e.g. on inner city African-Americans, or on the political stability of drug producing countries and the security of their peoples). They also tend to drop or evade constraints on the means they employ, for example dropping legal commitments against torture and for fair legal trials because terrorists are special. As a result, effective governments lack a proper sense of proportion or perspective.
When people talk about the dangers of big government they sometimes confuse these two aspects, which every government will have to some degree. But actually it is not the size of the state that affects its tendency to tyranny, but whether it is oriented to efficiency, where the people and their interests are in charge of what happens and how, or whether it is oriented to effectiveness, in which case it is the goals that are nominally in charge but the bureaucrats who actually decide everything. When one looks around the world one can see plenty of small governments (in terms of proportion of national GDP spent by the government) that are nonetheless tyrannical because that are focused on control - on being effective.