Finding The Essence In Portraits

This portrait of Diane was a challenge from start to finish. I'm hoping that this is now finished and I can leave it alone. First I procrastinated all summer to get it started then I kept loosing the illusive likeness that I was looking for. Some of my sessions with this painting I felt I got close, then on waking the next morning I saw where I had gone wrong.

I'm a long way from being able to dash these off and have likeness, essence and brush strokes that are loose and maintain their freshness. I may never get there but if I can find that something that I am calling essence at this point in time, because I don't know what else to call it, I am very pleased in the end.
This piece has gotten there in some measure for me and I dare not touch it further.