The Dark Side controls its followers?

It seems to me a dark side user is almost as if he \ she is possessed. They do have some control over their actions, but seem unable to do anything that is good or kind. Even the most evil person has some good in him, but when you're consumed by the Dark Side, that goodness seems supressed.

It's only Anakin, arguably the most powerful Jedi ever, who can turn to the light and resist the Dark Side, even though he's been in its clutches for years.

Luke resists the early temptation, but it's different in his case as he never turned to the dark side, he was only momentarily tempted, as was Obi-Wan.

Another thing that makes me believe the Dark Side controls one's actions is that Palpatine uses the hatred and anger to try and turn Luke, to join him, although common sense tells me if Luke is consumed with hatred, he will try and strike down Palpatine right after he strikes down Vader. Perhaps the Dark Side forces its victims to obey their Master - but only up to a certain point, because we know all sith eventually try turn on their masters.

Perhaps its a voice, telling them the will of the Dark Side, the same way Qui-Gon explains midichlorians telling Jedi the will of the Force.