"Need and valor"

[Zara]

No: HPFGUIDX 179582

zgirnius:
Dumbledore's portrait, in DH, "The Prince's Tale" tells Snape that he 
must arrange the transfer of the Sword of Gryffindor to Harry in such a 
way that Harry obtains it under conditions of "need and valor". Harry's 
instincts (DH, "The Silver Doe") seem to support this claim, since he 
feels it is important that Ron be the one to destroy the locket with 
the sword. Ron, of course, is the one who ends up retrieving the sword 
after the locket tries to kill Harry.

So now I am wondering. Why was Dumbledore, who came into possession of 
the sword rather straightforwardly when Harry gave it to him in CoS, 
able to use it to destroy the Ring? Was it because his own ill-advised 
action in putting on the cursed thing created the necessary danger?