I think humans bond in pairs because of this tendency. One's "partner" will probably not be that similar to you. So their influence, coming from outside your stagnant-fishbowl-thinking will create some imperatives. "Imperatives" is what the lone person lacks. Being free of outside forces truly creates stagnation. Doing things you don't want to do (you THINK you don't want to do) leads to new landscapes with more intrigue.
If for some reason a "partner" is not gonna happen, you can still give yourself up to an outside force (person or situation) that sets expectations for you, and from there you can't help but stumble upon new choices.