I have developed a very bad fabric hoarding problem lately, after getting back to quilting after a few year's absence. (No stash!) I decided that I had to give myself some boundaries in buying fabrics that I don't have a particular project planned for using it: 1) It has to be selling at a really, really good price. 2)It has to be exactly a color or pattern I could visualize using. 3)I have to be reasonably sure I won't find this particular print or something close to it again.
Then I rationalize and try to believe that the fabric meets all this criteria. But it works well in theory! If you can afford to buy it, you will use it someday - either sharing it with someone or planning a quilt around that fabric you just had to buy.