The improvement journey does not stop at habits. Getting good at consistently spending time and energy on things is only one side of the puzzle. The other side is ensuring the hours you spend are both efficient and effective.
Efficiency refers to the pace at which you complete your work, and time-boxing already makes a great start on this. Limiting the amount of time you’re allowed for an activity encourages fast action, and allowing slightly less time than you actually want can help you increase your speed. It is also useful to reduce downtime by preparing the environment in advance and using templates, scripts and automations to perform mundane tasks.
Effectiveness refers to the quality of your output and the amount by which you improve. This varies a lot per activity, but most can benefit from following a learning plan, reflecting on your past work to find issues, asking for help and advice from experts, and making quick iterations rather than getting stuck in detail.
There are many methods to improve efficiency and effectiveness, most of which are still unknown to the JSM, so anything that optimises them is fair game.