Comment by aubanel

In the collection of Rilke's letters "Briefe an einem jungen Dichter", he writes what I think one of the best advice about writing a book or not:

"This above all: Ask yourself, in your night’s quietest moment, Do I have to write? Dig deep down into yourself for the answer. And if it is yes, if you can meet this solemn question with a strong and simple “I must,” then build your life around that necessity."

It's harsh, but I think the necessity aspect is important: if you feel like a spring from which the urge of writing naturally flows and you could not repress it, then write. Else, don't.