I'm a fond reader of MMM (
http://www.mrmoneymustache.com/) too.
My thinking is that it is about determining what will make you
happy, and for me the answer is time. Material things (like cars or smartphones) genuinely don't interest me - so last night after work I was sat on the sofa, cool drink on the side, GF nearby, reading a lovely second hand book I picked up for peanuts - and I was genuinely happy. Some of my happiest days have been planting/digging veg in the plot at the end of my garden, or going for a nice cycle (all inexpensive hobbies).
So, I go to work (and sell my precious time for money) and then have a choice. I can spend that money on material things for now (which I'm pretty sure wont make me happier) or I can save/invest to have more time in the future.
In a few years, we may have children. At which time, saving will likely slow/stop. However, hopefully those early years of saving will give us extra options - like us both working part-time, one stopping work altogether, or me accepting a lower paid job that allows a better quality of life and more time with my family. Now,
that would make me happier than a smartphone.
