Learn to say 'I don't know.' If used when appropriate, it will be often.

The Secretary of Defense is not a super General or Admiral. His task is to exercise civilian control over the Department for the Commander-in-Chief and the country.

The worst mistake is to have the best ladder and the wrong wall.

Keep your sense of humor. As General Joe Stillwell said, 'The higher a monkey climbs, the more you see of his behind'.

There's another way to phrase that and that is that the absence of evidence is not the evidence of absence. It is basically saying the same thing in a different way. Simply because you do not have evidence that something does exist does not mean that you have evidence that it doesn't exist.

You will launch many projects, but have time to finish only a few. So think, plan, develop, launch and tap good people to be responsible. Give them authority and hold them accountable. Trying to do too much yourself creates a bottleneck.

From where you sit, the White House may look as untidy as the inside of a stomach. As is said of the legislative process, sausage-making and policy-making shouldn't be seen close-up. Don't let that panic you. Things may be going better than they look from the inside.