Of all of life's disappointments, one may be that writing novels is nothing like riding a bicycle. You don't learn how to do it, then jump on the old bike next time for another madcap downhill over the cobbles ride.
You have to learn again every time.
But it's very hard to admit that you've woken up and lost the magic touch. Sure, you're still good words. Sure, you still have a wry way of looking at things. Sure you still find people interesting. Sure you still have ideas and lots of them. But writing a novel is much than curiosity, talent or appetite, it has a rhythm of its own and serves up its own lessons as it will and novels are weird in the way they unfold so that it's only at the end of the first draft you know what it's about and can go ahead and safely write the first line.
A novel is the kid that won't tell the secret no matter how much you bribe it or theaten it. It's surly.
Every novel I've written I've had to learn to write one again, no less this time, but...