It's a strange combination... He got the investment income is the secret part, but then seemingly stopped at the earliest opportunity. It just seems lazy. I agree with him that spending more than you make is irresponsible, but I also think there's a happy medium where you can both have a coffee and a retirement account. You're not taking any of it with you anyways, might as well enjoy a few moments of it.
I think we have to be very careful in a society that promotes living in such excess. It's a hard balance to find between casting off all expenses to the point that it becomes frugality for the sake of being frugal, and frivolous-spending yourself into debt.
I think the great depression and the shortages of WW2 were hard on him in ways that I just can't know.
http://www.mrmoneymustache.com/2012/07/27/youll-never-be-nor...
Does being stressed out and anxious over driving a few miles and spending some money on ice cream really sound like a happy life? If you take spending to the extreme and don't live within your means, you'll be stressed about how to make ends meet and pay your bills. But at the same time, if you take frugality to the extreme, you're just trading that for being stressed over spending too much money.
Life is short. Be smart, keep a good balance and enjoy yourself.