A Curious Reluctance to Finish

I finished my first draft of book #5 of The Righteous series, Destroying Angel, several weeks ago, and have been puttering around with rewrites ever since. I feel like a runner at the end of the marathon who has decided to slow down and walk the last half mile, not because the tank has run dry, but because he has been training and running for so long that he doesn't want it all to be over. It's the last book of the series (with a possible extension on the table), and I've lived in this world and with these characters for so long that I'm reluctant to say goodbye. Or at least that's my excuse. The other answers are less satisfactory. There's no hard deadline to face--I'm ahead of the terms of my contract with Thomas & Mercer--and there's a certain reluctance to finish this book and move on to my next, which is the WWII thriller. I'm both excited by and terrified of that project. More stretching of the writer muscles, and I don't to pull anything. And then there's the excuse of my recent vacation, followed by a week of house sitting for a friend, with the distractions of spring all around. Or maybe I'm just procrastinating. The answer to that is always more butt in chair, fingers on keyboard.