And why is it so difficult to leave this plane?  

The removal of the spirit from every cell in the physical body that it has united with, is not an instant process.

I know you are living in time and this is a very different realm.  But it is a release of every cell and some are holding things that are incomplete and have blocked the forward movement of growth.

You are a small microcosm.  This is truth. You are a universe to yourself.  Each cell is separate and each energy that enters it that is of your spirit at the time dwelling within the cell, is separate.   You have seen in bodies where part of them will have necrosis, or parts are dying.  It does not mean that all are dying.  But some have chosen to move away. To maintain life in this realm that part of the physical body because the energy is what supports the life and the flesh and that movement of that vibration, you must remove it.

Then, there is the concept of the opening of spirit in body.  That beautiful tie, that beautiful knot that is made when you enter into the physical realm.  It is with twisting and tying and pain that it occurs for it is only in pain in physical worlds that you feel this.  But it is very much felt in the  beginning of the life and it is very much felt when you are undoing this knot.  It is the best way to describe it.

So, you must feel that pain.  It is the releasing yourself from it.  It is untying the knots that have held you here.  It is manifested in pain but the spirit feels it not.   For as you release you are higher, more separate from the body.  Like that new babe when you entered it.  That body shakes, it is wet and cold and so be you in spirit.  And the light is bright and so be you when you arrived.  And there to hold you and wrap you in energy and warmth are loved ones.  Yes, your mother often in both realms there in a cradle of awareness in spirit holding you and washing away the physical pain.  In great clearness there is no longer a veil holding you distant from those that are of a distance away.   All are present.  All are present in the physical and spiritual world. And there is a great reunion.

That is why many in your physical world feel the presence of the departed one. They feel them there and rejoicing and often there is laughter for there is great celebration.  I know you lack and want to hold the loved one during the experience of loss.  That is why there is pain.  It is not easy to untie the knot.