Time spent on a specific work will or should result in a good or decent amount of money in exchange.
I have seen the importance of time management because time is the only thing that is not in our power to change. Just like you rightly said, time lost cannot be recovered, that is why we must do our best to use our time wisely to avoid being in a situation of regretting how we use our time I the future.
The question, what are you doing with your time now? Let's reflect on this as individuals and make better use of our time.