In my (former) building at work, there was a small cafeteria. It was always so easy to just go there, literally 30 yards down the hall, instead of bringing from home.
At the new year, I made a resolution to cut cafeteria food to only 50% of my lunches. Yes, I know.....aimed low, but figured I'd meet that goal, then step it up later. I should have aimed higher from the start.
Anyways, I did the tracking spreadsheet to keep myself accountable to the goal. Early in the year, while still breaking the bad habit, I dipped as low as 62% from home, but improved since. I'm currently at 87.5% from home (98 home lunches, 14 cafeteria / going out) year to date, with the mentioned no cafeteria since June. (I work a P/T schedule, plus some vacation, hence the only 112 working days year to date). Previously I'd guess it was well north of 90% cafeteria lunches.
It is only a matter of keeping good lunch material at home - either dinner leftovers or good bread and sandwich fixings, plus fruit. I can whip up a great lunch in only a few minutes. If worked out to an hourly rate, the payoff of DIY lunch is big bucks per hour.
I've really noticed how little I actually spend in cash now, since I made this change.