Yarn Buyer's Remorse?

For the past few mornings I have looked in my closet and longed for a lightweight cotton sweater to wear in the mornings to keep the chill off. I could run to Target and buy one for cheap but the knitter that I am shakes that off and says "hey, I can make that!" The frugal knitter that I am doesn't want to spead too much on yarn so I go to Joann's and start looking at Sugar n Cream and Lion's Cotton for inspiration and walk out with 4 balls and no idea what to do with it. Then I start thinking, Do I really want a sweater made from washcloth yarn? How well will it wash? Why did I spend $20 on that when I could buy some Shine from Knitpicks or a whole sweater from Old Navy for the same price? I really see myself returning the yarn to Joann's tomorrow and then making a KnitPicks puchase. As my husband told me a few days ago, "It has been a while since you ordered from your place in Portland. Shouldn't it be happening soon?"