Here's how to recognize that your relationship is already over and it's time to let it go.

1.  You aren’t communicating.
Communication is vital for a relationship's success. After all, nobody's a mind-reader and expecting your partner to just be able to divine your wants and needs is a one-way trip to frustration and disappointment. However, there's a difference between communicating and “filling the air with noise”.

2. You're going from fight to fight.
Going from fight to fight is a surefire sign that something has gone horribly wrong at the core of your relationship and neither of you are managing to address it.

3. There's no trust (and nothing gets forgiven).
4. Nothing ever gets resolved.
Of course, not all conflicts in relationships look like fights. Sometimes those conflicts are the absence of progress, where no matter what you do, nothing ever changes. You can talk until you're blue in the face. You have discussion after discussion after discussion.

Maybe they're trying to keep control in the most passive-aggressive way possible. Maybe they just don't care enough to change anything. Doesn't matter. Whether you can't or won't address the underlying problems, the best thing for both of you is to make a clean break of it.

5. You want it to be over.
Many people linger in broken or flatlining relationships because they're looking for something they can point to as a reason to leave. Ironically enough, this is the surest sign that the relationship is over; it's over because you're decided it is.