You can write any time people will leave you alone and not interrupt you. Or rather you can if you will be ruthless enough about it. But the best writing is certainly when you are in love. If it is all the same to you I would rather not expound on that.
So that's why one of my rules of parody writing is that it's gotta be funny regardless of whether you know the source material. It has to work on its own merit.
A serious writer is not to be confounded with a solemn writer. A serious writer may be a hawk or a buzzard or even a popinjay, but a solemn writer is always a bloody owl.
Except I'm aware that as a writer you can't get away with as much writing for children as you can with adults. Children have much more finely tuned senses of justice, morals, and ethics. They are much more Platonic: children are symmetrical, before we begin to fragment them with our own nonsensical ideas and squelch their natural joy in knowledge.
The old incapacity. Interrupted my writing for barely ten days and already cast out. Once again prodigious efforts stand before me. You have to dive down, as it were, and sink more rapidly than that which sinks in advance of you.