Half of self-improvement is measuring
What is one of the most successful tools in the history of self-improvement? Hint: It's right under your feet. It's the weighing scale. Accurate measurements are the easiest way to create a self-improvement system that adheres to the principles of flow. By having numbers, then you have instant feedback that your self-improvement project is working. If you see even just a slight quantified improvement, then it's incredibly encouraging.
Asking "How do I measure this?" is the first crucial step to building any successful self-improvement program. If you're trying to become happier, for example, do you have an accurate measurement of your happiness? You could, for example, count the number of minutes you spend per day lying on your bed, staring at the ceiling, twisting and turning your worries in your head. You could count the number of neurotic episodes you have per week. Then when you try cognitive therapy or meditation, you could measure yourself again and see if you've made progress.
Measurement can open the door to a dimension of self-improvement that you may not even know existed. For example, how do you reduce the friction in your relationships (professional, romantic, or platonic)? While you could measure the outputs, like the number of times you get into a fight, the pattern may be too irregular for you to get meaningful feedback. Even better is if you can measure the inputs.
The Josephson Institute has a concept called The Six Pillars of Character, whereby they define character as Trust, Respect, Responsibility, Fairness, Caring, and Community. You could then measure you and your partner's response to a conflict according to that rubric. How caring was I in that scathing email that I just sent? How reasonable are her demands on the relationship? Anecdotally, my personal conflicts became dramatically reduced when I delved into this kind of exercise.