To improve you have to measure. Without measurement, you have no way of telling if you are improving.
There are subjective measurements such as giving yourself a number from 1-10 for things like happiness, fulfillment, focus, etcetera.
The numbers don’t have to be accurate they just have to be consistent. It is the trends up or down that is relevant. Moving your focus from a 1 to a 3 is just as good as moving it from a 7 to a 9.
There are quantitative measurements that are concrete such as weight, # of days doing a habit, and income. While quantitative measurements are factual, it is still the interpretation that is subjective. Typically many quantitative metrics need to be compared.
Without the metrics, you cannot have the interpretations and it is the interpretations that are valuable.