I don’t know how other authors feel when they finish a book. But, having written quite a few now, I can tell you how it usually goes for me.
First, I let out a long sigh of relief. It’s a lot of work to write a book, and it’s nice to have that work done. The same with any big project, really. Lots of work, lots of pressure, and then—big sigh—it’s finished. I don’t throw myself a party or anything. I don’t pat myself on the back. I just hit “send” on that last thing and then, Ah, whew.
Next, I enter a recovery period. Nerves are frayed from the final push. Fingertips are drummed to red. Diet and daily schedules have been sub-obtimal for a civilized human being. The synapses of the mind are crispy fried from focusing fretful day and fitful night on The Book. It takes awhile to let it all go.