Once you become experienced at saving money it can be hard to ignore a good sale opportunity. Getting a deal can be addicting, but it is no longer frugal when you buy such a large number of one type of item that there is no hope of your using it before it goes bad, or you don't have room to store it.
As an example I have purchased enough deodorant to last my family for a year. Now I pass up great sales on deodorant, no matter how tempting they are, unless I get them for almost free and I plan to donate them. When our supply gets low I will again buy deodorant.
Another example is when someone I knew discovered thrift stores. She enjoyed saving so much that she ended up spending more money on used clothes than she would have allowed herself to spend on new. She had become addicted to the process of getting a good deal.
Learning to use and stack coupons and shop sales is wonderful, but know when it is appropriate to say, "I have enough".