I had never planned to retire (mostly because I loved my job), even though my wife started bugging me about it after she retired in 2000 with an early-out opportunity. Then, in 2005, we lost two good friends (separately), in their early 60's. At the service for the second, I decided I did not want to "die at my desk" and told my wife I had decided to retire when I turned 62. I went through some of that same uneasiness, but felt I was prepared because we had paid the house off 10 years prior, and carried no debt other than monthly stuff that we paid off when the bills came in.
I retired Jan. 2008, and have never regretted it. Miss the people from time to time, but found that serving as a volunteer business counselor helps me stay in the business world a bit, and I enjoy helping my clients. Staying active, doing what you want on your own schedule, is, IMHO, one of the keys to successful retirement. The others are financial preparations, and staying as healthy as possible.
Congratulations on your decision! May you spend as many years enjoying life as you did working! Happy retirement and good lunting!