Although it may sound a bit "preachy," I really feel that society has become somewhat pathological. Money seems to have become the only standard by which people are measured, and everyone is desperately chasing wealth, as if without money, you have no value. Meanwhile, the things that should be most cherished—character, sincerity, effort—are being pushed to the sidelines. People are so focused on counting their money that they forget what truly matters: how they live and the kind of person they become.
Don't forget, money is just a bonus that comes after the realization of self-worth.
It is actually a worthy piece of advice in two ways. Firstly, it's worth recognizing burnout, which can happen when you are spending too much time working - it can be ok in the short term, especially if you are getting juicy overtime opportunities, but if you try to do too many hours over a long time it is going to ruin your mental and physical health. Be kind to yourself and let your body rest for a bit, because you cannot spend that money if you run yourself into an early grave. Secondly, people can pick up jobs that reward you very poorly for your time, when you'd actually be better off learning or simply enjoying a rest for your main money earning ability - always be re-evaluating if what you are doing is worth the payoff in terms of dollars per hour after all real costs are counted.