One pretty major sign that your relationship might be stale is that you and your partner aren't as intimate anymore. "You avoid or have simply settled for no romantic involvement," Brown explains. "You don't even cuddle or hold hands anymore." Being physical, in any sense, can be a huge part of a relationship.
not fresh; vapid or flat, as beverages; dry or hardened, as bread. musty; stagnant: stale air. having lost novelty or interest; hackneyed; trite: a stale joke.