Were the Istari Unable or Unwilling...

[Sardy]

I just read a great piece in Unfinished Tales that (to me, at least) seems to shed a little light on the nature of the Istari and their conscious recollection (or lack thereof) of their past lives, true natures, and mission...

Gandalf states:

""To do that I used in my waking mind only such means as were allowed to me, doing what lay to my hand according to such reasons as I had. But what I knew in my heart, or knew before I stepped on these grey shores: that is another matter. Olorin I was in the west that is forgotten, and only to those who are there shall I speak more openly."" (my bold) --Unfinished Tales, The Quest of Erebor

It would seem that the Valar, in sending the Istari forth, actually had curtailed and dimmed their memories of their true nature and essence... allowing (and necessitating) them to have a more "earthly (or Middle-earthly?) sympathy to their task at hand.

I would go so far as to think that we might readily replace, "...and only to those who are there shall I speak more openly." with "...and only to those who are there can I speak more openly."