Writing requires discipline, but disciplined writers are not necessarily prolific. Most good work gets produced over time, sometimes many years, allowing the writer to grow with the material, to allow her world, her command over craft, and her psychological maturity to coalesce at just the right moment to produce something of value. This process often involves dreadful periods of not writing, or, worse, periods of writing very badly, embarrassingly badly. As time passes in a writing life, the writer learns not to fear these arid periods. The words come back eventually. That’s the real discipline: to train the mind and heart into believing that words come back.
Be willing to wait. In the meantime, write when you don’t feel like it. If you can’t write, read.