Meaning of the phrase "Relax Into The Pain"

Quite often I have come across this phrase - Relax into the pain.

We can treat a pain but how does one relax into the pain, especially if it's an emotional pain, for example grief?

Can anyone please explain what does this phrase mean?

Pain causes anxiety because the patient is anxious for the pain to cease (and anxiety reinforces pain). People cannot relax when they are anxious, even if they are at rest. The suggestion here is to stop fixating on the day when the pain will cease; it will cease when it will. Instead, turn your mind to other things so that you can relax.

In the context of static stretching, the advice I've heard is to hold the stretch for quite a while, ranging from 10 seconds to 1 minute. There is often a point at which the stretched muscle relaxes slightly, allowing a greater range of motion. (Note: don't try this at home before getting appropriate advice.)

When a therapist (physiotherapist, occupational therapist, etc) stretches a patient, the period prior to that point of muscle relaxation can be quite painful and possibly alarming. Since the muscle is already taut, the reflex action of tensing the muscle doesn't help.

The advice to relax into the pain might have been given in that context to encourage the patient to endure that initial pain. The metaphorical use of that advice when applied to grief or other emotional pain might be motivated by analogy. The question of how one relaxes into that sort of pain, however, is likely to be very personal and to depend on the individual's circumstances, and therefore out of scope for this forum.