Isn’t it interesting how fear of failure motivated you, and yet for other people it makes it very difficult to get started. The main thing is that you found a way to use your fear to motivate you.
Maybe what distinguishes the two situations is whether your fear was of failure to get the book done, and (and so your fear spurred you on) or whether your fear was of the book not being good enough/no one will like it. That second fear might have made it harder to start or work on. What do you think? Did you have a mixture of both?
Wonderful rewards! I wish you a house FULL of plants and lots of dancing.
As for your reward of Sit and think about the feeling of completion, I suggest that you want to go beyond thinking. You want to bask in the glow of completion. Feel your chest expand in gratitude toward yourself for completing it. Sit and FEEL your happiness.