This question originally started out as an answer on Quora. I thought it would be appropriate to copy it here.
How do you keep a relationship from getting boring, dull, losing the shine? That’s easy. The answer is contained in the question. Don’t let the relationship become a routine.
It’s not inevitable that relationships become routine. They can remain novel and exciting for decades. They become routine because the people involved choose to make them routine…often without even realizing they’re making a choice.
You know how Yoda talks about the dark side of the Force?
How he says it’s faster, easier? That’s a relationship becoming routine. You make little choices every day because doing the same thing today that you did yesterday is just…easier. Falling into patterns is just…easier. Assuming certain roles that you repeat in the relationship is just…easier. You do it without even thinking about it.
But you don’t have to if you don’t want to. It takes more conscious effort, but you can have a relationship that doesn’t settle into a rut, that stays novel and engaging.
Not everyone wants that, of course. For some people the routine of a relationship is comforting, maybe even part of the point of the relationship.
So that’s where compatibility comes in. If you are a high-threshold, high-novelty seeker, date people like that. Don’t date people who want a comfortable, steady relationship.