Good Example of this:
I thought I was doing good by not buying coffee out and making my fancy-pants lattes at home saving:
Coffee out monthly 110.00 would need an extra $33,000 in my stache (this is the Latte factor, folks!)
But, like any good Mustachian I make my own at home, good, right? Until I realized I was spending 50.00 a month in milk, just for coffee because instead of one coffee a day out, I'd drink several, it's cheaper! I'd need to add $15,000 to my stache to cover it.
Now, I've gotten used to drinking it black, and don't have all the health issues I get with Dairy, and for a mere 15.00 a month, I only need to add 4,500. Is coffee worth that? Or would it be better to remove it completely and eliminate the expense? That remains to be seen.
The power of this concept is when you start to examine ALL your little choices, how much they add up to together, this is how you literally shave YEARS of your FIRE date. But, you still want to enjoy that time, so what trade-offs are worth it for you?