Towards the end of A Wizard of Earthsea, when Ged and Vetch/Estarriol are pursuing the shadow Ged says:
I have followed too slow. It has found the way to escape me, and so doom me. It must not escape me, for I must follow it however far it goes. If I lose it I am lost.
But I can't work out what he means. As far as I can see he pursues the shadow towards the ultimate meeting just as he was already doing, just slightly faster. Is it mentioned anywhere in the book or Ursula Le Guin's interviews etc what Ged means by "It has found the way to escape me"?
Thanks to everyone who answered, but I don't think anyone has go to the heart of the matter, probably because it was either a slip or a whim of Le Guin's and there is no answer. I reread that bit of the book, and it is clear that prior to Ged arriving at Astowell are pursuing the shadow as fast as they can (without using a mage wind). He is confident of the pursuit and indeed says to Estarriol:
Is the iron sure where the magnet lies
They stop overnight at Astowell to rest and fill the water skins, and it's in the early hours of the morning that Ged makes his statement. They then continue the pursuit as before, but this time using a mage wind to drive the boat faster. There isn't any indication that Ged has lost the trail of the shadow, or of any other change.
I suspect this may simply have been a dramatic device. Having the travellers stop at Astowell allows Le Guin to reinforce that this is the edge of the known world, and the sudden urgency gets the travellers away from Astowell in a dramatic fashion. Unless Le Guin herself comments on the matter I think I'm stuck.