I just started working towards ER a few months ago and it's meant a pretty major change in my spending, and a pretty major change for me personally too. I've told my close friends and family that I'm working to pay off my student loan this year, so they will understand when I don't want to go on expensive trips or back out of certain activities. I haven't really talked about saving for retirement as the reason I'm doing this.. people seem to understand paying off student loans as being a pretty normal goal, especially when they're 6.7% right now.
That'll be done this year. Next year I want to max my IRA(@ 20% of my take home), so that's another common sense reason for not spending much. When I get in to a higher paying position at work it's going to be about saving for a house, then paying off a house, then maybe saving for kids education, or working to buy another property or invest in something tangible. I think all of those are things that people can relate to, or have lived through. For the typical consumer, doing any of those would mean every spare cent is going there, but with my low funds required to live, I believe I'll be able to save substantial amounts in investment accounts for the same time. If I time it right, I'll be FI just about the time I run out of excuses not to spend :). I'm comfortable giving people a story that makes them feel they understand what I'm doing, but what I'm ACTUALLY doing is really none of anybody's business except mine. And strangers on the internet.