In a recent post: http://www.moodscope.com/blog/life-as-an-accomplished-marathon-runner) I suggested pain signalled injury and was a good reason to stop running. Several people commented that some pain could be safely ignored and some pain was necessary for growth.
The critics are right, without a thoughtful definition of 'pain', the rule 'Pain equals stop' is simple enough to limit injury at the cost of limiting growth. The trick is awareness. Before deciding to push on or stop, you need to know what sort of pain you are in.
Many running authorities say STOP level pain is:
1) Persistent sharp or stabbing pain.
2) Pain that changes your gait.
Physical pain that changes your gait is probably the most relevant parallel to emotional pain that changes your mood. Combined with pain, gait changes are a sign of injury because your body will protect you by using uninjured muscles instead of injured ones.
The problem with ignoring this is that the uninjured muscles aren't built to take on this extra load. For example, ignoring hip pain tends to injure your knees.
Even if your mind won't acknowledge pain and injury, your injury can be seen in your gait. Often I'll make myself believe I am healthy, but my spouse will say "You are limping."
Be aware of yourself or accept the observations of trustworthy friends. You can distinguish between injury and growth. You can rationally decide what must be acknowledged and what can be ignored.