Until discovering MMM a few months ago I was in the camp that small items like buying a daily coffee at work do not make a big enough impact to justify doing without.
Since then I stopped and only drink the free work coffee. I realized it's not the one daily coffee, which is actually not a big deal by itself, but all the "little things" as a whole add up quite a bit.
I am still not very mustachian compared to most on this website but trying to move in that direction.
FYI - don't miss the daily coffee at all now that I stopped, the free stuff seems perfectly good to me. Same with other little changes, none of them seemed like a hardship once I did them.