There's a whole range there. You don't have to live on ramen. But you can be really aggressive about insurance premiums, utility bills, etc. You can learn home & auto repair & maintenance. You can make major life structure choices (Can your family live with one car?). These all can make a huge impact on your finances, and don't hurt the way perpetually living like a college student does.
Counterpoint: Your chances of dying before "making it big" and retiring are somewhere in the 1-in-10 range.
If this is the "get rich without getting particularly lucky" advice, perhaps we should assume it's also the "get rich without getting particularly unlucky" advice. There's an endless list of terribly unlucky things that would ruin just about anyone, but don't generally bear planning for.