To be satisfied with ones self.
The kid was complacent with his small little trouble free world.
The hippies and lazy teenagers were complacent, complaining but never doing anything about it, never realizing they were part of the problem.
The complacent protestor held up a sign and screamed chants, complaining a lot, but never took any positive action to make a change.
The old guy became complacent and got a bunch of diseases because he didn't take care of himself, lacking the motivation to do anything with his waning years.
When you notice that some small aspect of reality has suddenly changed from what you thought it was, like in the Star Trek: TNG episode Parallels when Worf silently switches between alternate realities.
Sean: Whoa, since when have Disaronno bottles been rhombuses? I thought they were rectangular.
Liam: Dude, they've always been rhombuses.
Sean: I think I'm worfing.
Worf: I... I thought the cake was chocolate.
Troi: Don't I wish!
Worf: Counselor, the painting that Commander Data gave me, it has moved.
Troi: Worf, I hung that painting there at your birthday party, remember?
The painting has changed! Don't you see it?
Your hair, and your clothing, they have changed as well!