How to know if you have capacity in your nervous system to feel and integrate an issue?

Healing is non linear. And we cannot put these things in a box using rigid rules.

The nervous system changes moment to moment.

It's important to know your own body in a state of safety and in all others states for you to start to recognise the difference in yourself.

Many people think they can do deep healing work on their own (I used to think that myself). 

This in itself is a trauma response.
We need a professional who knows how to titrate the process, co-regulating with us, mirroring safety to us and the other things we don't really recognise in ourselves, somatically, so that we can start to learn to identify all these states, in an embodied way. 

Safety is a felt sense. In very simple terms physiology of safety is the absence of fight/flight/freeze/shutdown. You have just enough of sympathetic activity in your system to feel aliveness, without feeling stressed. Rest and digest, connection to others etc...But these are just words. 

The felt sense of safety can't be conveyed in words. People with a history of trauma don't know how to recognise safety accurately.
Many never ever felt safe before. The missing piece is the felt sense.