First draft blues--or is it relief?

With the first Blue Plate Mystery, Murder at the Blue Plate Cafe, just uploaded as a digital book to various platforms, I just yesterday finished the first draft of the second in that series. So far I'm calling it Murder at Tremont House, but that's tentative. (Kelly O'Connell fans, don't worry: A Kelly O'Connell Mystery, titled Danger Comes Home, will come between the two in the new series, next July.)
Meantime I'm trying to analyze how I feel about finishing that draft, after many nights of lying awake with plot threads going through my mind. Most writers feel great joy but I didn't. I think the biggest feeling I had was relief, as if a weight was off my shoulders. I knew how it would work out--and it did. I think it's okay but such a decision is far down the road. I also feel a bit blue, like I'm saying goodbye to characters I've lived with for a long time. Of course, that's silly--I'll be going back to them a whole lot in the months to come. But it's a funny feeling, almost like I should start the third book in the series right away--which is of course the last thing I want to do.
Next step is to send it to my favorite beta reader. His critiques are thorough, to the point, and offered without mercy. He always finds the good, and then digs in and tells me what bothers him in a work. He's priceless. But he's out of town, so I can't whisk it right off to him.
Besides, I have one final scene in the epilogue to write--no, please don't get me involved in a discussion of whether there should be epilogues or not. I like to end the book on a fairly dramatic note and then tie up the loose ends. And I've done all but one "loose end"--it maybe the hardest scene to write because it will irrevocably change the direction of the next Blue Plate Mystery. At any rate, I find myself dragging my heels about the scene. Tonight, I've promised myself.
I read a Facebook post tonight by a writer who had cut her first draft from 115,000 words to 107,000 but still had scenes to write. She said she doesn't know how anyone writes a 65,000-word novel. I do. This one, in draft, will probably come out about 62,000 words. I long ago faced the fact that I write short. When others moan that 450 words isn't enough for a book review, I sometimes wonder whatever I can say to take up 450 words. Maybe it's a blessing. I've know writers who, when asked for four pages submit twenty and act wounded when you request cuts.
Meantime, the age-old question: what am I going to do with myself while waiting for the critique? Maybe go back to the book of blog posts that an editor suggested. It's my fall-back project, and I can't be without a project.
A TCU English major was assigned the duty of interviewing an author and her teacher suggested me. She came by tonight--a delightful young woman--and one of her questions was, "Why do you write?" My answer? "Because I can't not write."