In a book I have been reading from Brian Tracy, there is a section dedicated to Self Discipline and Personal Excellence, and in that section, I found a little piece of advice that I think is very valuable.
He says “Invest the 3% of your income back into yourself”, in practical terms he says that you should invest 3% of your desired earnings (not your current earnings) in books, courses, seminars, and other educational materials that allow you to increase your expertise, in terms of skill and knowledge and grow in your field.