Be prepared to tackle your manuscript in multiple revision iterations.
Maybe one day, you revise the entire thing with a focus on word choice. Then, the next day, you do a read-through and edit to focus on historical accuracy. Stay focused on the areas you’ve marked for improvement and special attention. Be patient.
You might be midway through your outline and realize you need to do additional research or watch a movie that people recommended as a reference. Do it.
Don’t let the pressure to put out a follow up to your first well-received work push you to a hasty release of the next piece.
If you’re honestly working to improve, you must work as hard as you did the first time, so you can reach the level of quality you’ve already set for yourself. Then, push at least 25% past that. Work harder than you’ve ever worked before; the improvement will show.