What I'm about to say might be controversial. It goes against the grain of the 'Look at me I'm so frugal' meme/arms race here on HN.
The financial crash of 08/09 left such a bad taste in my mouth (as in I lost many tens of thousands of dollars) that I have completely lost faith in the stock market and anything associated with it such as ETFs, mutual funds, 401k, etc.
Getting a 'real' job and putting money into my retirement accounts lost me tens of thousands of dollars in savings (so think about how much lost time that is) and the job that paid for it all. Yes, it absolutely sucked. I was furious, with myself, with others, with my parents (who advised me), etc. It was a terrible time. I drank.
I was forced into doing a startup in Dec. of 08. It's been profitable since the first month. You would be surprised at how well you can focus when you lose your job and half of the money in your bank accounts in the course of one business quarter.
I now keep large cash savings, put a small amount into my retirement funds, invest the majority of my 'extra' money back into my startup.
I bought myself an expensive Porsche, an expensive condo, and started spending WAY more on luxury goods / eating out because losing $XX,000 after being 'responsible' makes you realize how TOTALLY unpredictable this life is, especially when it comes to financial matters.
After working about 3x as hard on a day-to-day basis and changing my spending habits to purchasing much more expensive things, I now have way more money than I ever did (in cash and cash equivalents as well as equity in a business). Go figure.
This post isn't advice, it's just an honest recollection of the financial transformation I went through in the past 2.5 years.