Congratulations!!!!
I agree with SWO1.
I was in the civilian work force for 48 years. The biggest adjustment was emotional. I've always worked hard and placed much of my daily net value in what I had achieved that day. Had to adjust to the fact that my personal net value was based on who I am, not what I could do.
At first, it seems like an extended vacation. Whether or not you find a "keep busy" job or find lots of projects to keep you busy is your choice. My advice, just don't fall in love with a sedimentary life style.
Certainly wish you the best. Enjoy!!!