Another angle is that sometimes we also should be investing into ourselves in ways that would potentially cause us to work smarter rather than working harder and also we might be able to increase our income by being able to get higher paying jobs by investing into ourselves (such as training, education and/or getting experiences that might not pay well in early years, but have greater potential to pay off higher at later times down the road).
Updating oneself or improving oneself is a sign of a wise person. A wise person always strives to improve himself and must invest in it. Investment here does not mean that you have to invest money, sometimes you have to invest time to improve your skills, sometimes you have to invest labor, investing time can improve your skills and sometimes you have to invest labor, time and money. have to do Investing in yourself never hurts when it comes to investing, of course your knowledge will increase, it's a return on investment and your salary is likely to increase or your earnings will increase as a bonus for you. So always try to update yourself and invest some time in it. Investing in yourself can help your portfolio grow faster.