As someone who followed this advice excessively, I have to counter it a bit. Through most of my 20s I lived in the cheapest, shittiest apartment I could find, ate cheap (which in the US means extremely unhealthy) food, rarely went out partying with friends, never went on a vacation, never dated, etc. This kills your network and your health. Frugal is fine, but don't be so freaking cheap that when you're 30, you hate your 20s, and need to spend 2 years fixing your life.