Know you're about to do something stupid if you tell yourself 3 little words

Carl Richards / Behavior Gap

"Just this once."

Carl Richards, financial planner and author of "The One Page Financial Plan: A Simple Way to Be Smart About Your Money," highlights this seemingly harmless phrase as an indicator you're about to make a dumb - and potentially expensive - decision.

Thinking about the sales retailers offer for Memorial Day and the shoppers who flock to them so as not to miss a deal "just this once," Richards explains the problem with this pattern of thinking.

He writes:

In theory, we could plan in advance and save the money to buy a new barbecue or deck furniture that weekend. But for a good chunk of people, they wander into the store, telling themselves they aren't really there to buy anything. They just want to look around. They manage to stick with this goal … until they see something they want.

Then, they say to themselves, "Just this once …" only this time probably isn't the first time. It also won't be the last time they buy something based on an excuse.

Look, we know all the sales tricks (e.g., buy now, pay later), but we're bad at remembering these tricks work on us, too. Of course, there may be some great deals. But we need to be honest and ask ourselves if it's the best deal or if we're using it as an excuse to ignore our budget. We can't keep counting great deals as one-time events if they keep happening.