Wielding the light though is not something anyone can do.  I believe it is stressed that it is an act ‘will’ rather than faith or belief.  It is something reserved for the leaders, or potential leaders of forsaken society, and  I’m fairly sure there would be a vetting process to determine whether an individual is stable enough and has the capacity to embark upon the undertaking safely.
Feel blessed that your spirit was not released to the nether.  Feel even more blessed that I decided you were worth the effort to write this scroll for you.
The people you once knew, perhaps even cared for, are no longer.  You must learn to live with that for the rest of your now unnatural life.  I suggest you learn to deal with that first.
If you think you are ready for the trials ahead then seek me out in the church in Deathkenell.
-Priest trainer Duesten-
He goes on to say.
… allow me a moment to explain a thing or two before you decide its time to seek whatever drives you forward; the holy light no longer concerns you, the spirits of your forefathers were fairy tales, and creatures of the nether don’t want you.
Do you understand me so far?
There is only one thing you must know.  We have survived through will alone.  It is faith in ourselves that separates us from others, and with our powers, we will cause great change in all of Azeroth.  The weak will come to lean on you.  The lepers will call you Lady/(Lord).  And the ignorant will look to you for guidance.  It is my duty to make sure you have the necessary tools, so when the time comes, you are prepared.
So what that implies to me is not only do the forsaken access the light in a manner different to most other people, but also that everything they previously knew and understood from their past life is irrelevant, an impediment, and can not help them in their pursuit of greater understanding, or pursuit of power.
Just for the record here is another sample of the foresaken attitudes to their previous lives.
William Saldean – Grain and feed vendor
I was here visiting relatives when Lordaeron fell, and then … well.  I suppose I won’t ever be returning to Westfall, now.
Sometimes I wonder if my family is still alive.   More often, though, I wonder why I no longer care.
The point I am trying to get across is that for the forsaken, is that embracing who they are, and not dwelling on who they were is as important an aspect of forsaken identity as freewill.