Chris Bailey and James Clear, author of Atomic Habits, discuss habit formation.
One of the points Clear stresses is the simplicity of habits. For instance, “writing” as such is too complex an activity to fit Clear’s definition for habit.
Clear instead focuses on habits as they can be performed with mostly unconscious operation. So, to develop a regular writing practice, you might particularly work on habituating something simple that will trigger the start of a writing session (e.g., getting a cup of coffee, leaving open the document you need to work on the day before).
For the full discussion, visit the Life of Productivity podcast.