I used to think the same thing, but I have been amazed at how busy I can keep myself --keeping up with the almost endless chores and busy work that I can find for myself.
The only difference now is: I can start and stop whenever I choose and now I can take naps at any time of the day with no one to tell me any different.
Still seem to get a whole lot done... even at my own pace. Trust me, time and age has a way of making retirement far more desirable as you go along.