Dumbledore is brilliant, talented, charismatic. People seek his advice, many follow him and risk their lives on his orders and believe he is infallible. All this placed a great responsibility on him and convinced him that he must make decisions for others. The Minister of Magic should follow his advice on fighting Voldemort, his spy, Snape, has to risk his life for information, the Order and Harry should trust his decisions without lengthy explanations and so on.

Being in such a position he was probably afraid that if he would appear unsure in himself and admit he made mistakes, saying: 'I am easily corrupted by power. My desire to find the Hallows and reform society for the greater good with my friend Gellert Grindelwald last time cost me my sister' he would lose the support and respect of his followers, and he won't be able to control guide them. Dumbledore once said that Voldemort has no friends, only followers. It's the same with Dumbledore. He thinks himself intellectually superior, the only one who can master a plan to defeat Voldemort. He never discussed his strategy with anyone: the only one who knew the finer points of Dumbledore's plan was Snape, and he wasn't offered much choice either, Dumbledore never asked his opinion, pretty much just ordered him to carry out his instructions. Dumbledore certainly seemed to think that's the only way to do things: working on his plan alone, in complete secrecy, never trusting anyone more than necessary, giving only the essential instructions to follow.