Our 'self-interest' demands that we help them. [=it benefits us to help them]
They acted out of 'self-interest' and fear.
(..) War is a horror that should be ended at once. I can't do both today. You are wrong to trust these men. I don't trust the Masters. I trust their self-interest. They're trustworthy if they're convinced that working with me is in their self-interest. You don't know them. You don't understand them. (..)2016 TvShow: Game of Thrones Title: Book of the Stranger Season: 6 Episode 4