Know how to read and explain a balance sheet. Private sector employers have very different objectives from those you're used to, and they will expect tangible results from you. Remember that civilians consider salary a very private matter. Dress for business. I underestimated the importance of this.
Civilians also have a different conception of personal and organizational loyalty.
It's better to get promoted because you exceed expectations than to get fired because you don't measure up. Adjust your expectations for your next career to the reality of your capabilities and marketability. You will succeed but not without adjustment. Planning for it is the most important part of the process. When you hang up your uniform, be proud, but put it in the closet, and make sure you keep your ego in the closet with it.