Parts of the writer’s life are as follows: desire to write, research, writing, promotion of a book, and there may be others. Each part requires commitment, but it may be that a writer finds commitment easier in one part than another. For example, does one have enough sense of  entitlement to promote one’s book? Is one committed to the promotion? I guess if there is any hint of reservation in any of these parts then it may be best not to do it and don’t waste a publisher’s or your own time. Sick to what one is committed to and work the rest out from there.