"You never, ever, ever second guess yourself when you’re the boss. You can’t afford to."To which I say "Nay!"- Matt
If you don't have someone to second-guess you, you will make the same mistakes over and over again. Yes it is important to stand to your decisions as a guild or raid leader, otherwise people will lose all respect for you. But you can't do everything right. As much as you think decisions through beforehand, you have to accept the fact that you will make mistakes. Making mistakes is human and isn't a problem at all, the problem is when people don't learn from their mistakes. But how would you ever notice your mistakes without being second-guessed? You can't.
The best way to solve this is to have other players around who second-guess your actions. You make a decision, but when others approach you on its validity you must be willing to consider that you were wrong. You must decide whether their allegations have any merit and compare their solutions to yours. You have to second-guess yourself. You may decide that your decision was correct and stick with it, which is fine, but you have to consider the possibility that you could have been wrong.
That said, don't brood too long over these issues or you will, in fact, end up with grey hair at the age of 21 as Matt predicted. If you disagree with those approaching you, tell them that and be done with it. If they continue to nag, tell them you have considered their arguments but they have not been sufficient. Then they either bring new arguments, stop nagging, or get silenced.
If they are right on the other hand, admit your mistake and lay out how things will be handled in the future. Only rarely will a reversal of your old decision be possible - don't try if it's not a very apparent fix.
A good leader can force through his will. A great leader is powerful enough to admit mistakes without hurting her position. Always try to be the latter!
I'll leave you and this unusually short post with a quote from George Bernhard Shaw.
"Success does not consist in never making mistakes but in never making the same one a second time."- George Bernhard Shaw