This is always the right question to ask. Always, in whatever we are doing, where ever we are in life, whatever our circumstance, we can profit from asking this of ourselves: "What will I do next?". We can also ask it of others--when we want, need or hope they will do something. Mainly it's a good question to ask yourself.
When you're feeling down: well, what will you do next? It's a great question that helps you refocus on possibilities and the things you hope for in your life.
When you're stuck in your writing: well, what are you going to write about next? One can get lost or overwhelmed by thinking about how big a project may be, but if yu focus on what you're gong to do next (in an immediate sense), you can make some incremental progress.
We can ask "what will I do next" on the large scale or the small. We can make plans for the next decade, the next year, the next month, the next week, the next day, the next hour or the next minute. It's difficult to make plans for the next second unless you think really fast. If you're getting stuck because you answered what to do next on one level, you can always try answering on a different level--smaller, more immediate levels are usually easier to answer.
It's a good practice to ask this question repeatedly, because as we learn from our actions we may want to revise our plans. The ability to revise our plans can be crucial in learning to overcome obstacles and in learning o break out of negative repetitive patterns.