How do you know when it's time to leave a relationship?

I have a very simple indicator for when it’s time to leave.

How do you feel about yourself when you are with that person.

Notice, I am not asking, “How do you feel about the other person or the relationship?” But rather how do you feel about yourself — are you comfortable or anxious, are you sure of yourself or always questioning yourself? Do you feel okay with other people but more self-conscious when you are with your significant other? Are you a bit nervous or vigilant? Do you doubt yourself more? Are you defensive?

This inside ‘thermometer’ of your own sense of self when you are around your partner should point you in the right direction.