I came across this post by Consumption Rebellion about the concept of 'Joyful Consumption' and it really rang home with me. I really encourage you to give it a read, it's about the idea that most people buy things to make themselves feel better, but since buying is pretty superficial it can result in negative emotions. Check out Eilleen's definition of Joyful Consumption to combat it.
I used to buy a lot of junk. I'm not exaggerating by using the term junk - it really was, because it was cheap and nastily made, and I had no idea about my style so I would buy something and then um and ah over it and never wear it out because I no longer liked it. I shopped to make up for things lacking in my life. I made impulse purchases, and I had no idea what I wanted to wear, only what chain shops wanted to sell me. I didn't know about fashion blogs or Flickr for inspiration, and magazines I read all had the same trendy stuff. No wonder I was confused - nobody had told me that fashion is self-expression. To me it seemed like it was just another way you had to fit in. I learned better but it took me a while.
These days I still have the urge to buy things to feel better. Sometimes I give in, but it's generally of the second-hand variety, and I (usually) have the excuse that it's for Heidi & Seek. I barely ever buy things I haven't planned to buy from chain stores, and it makes me happy that they don't influence me as much as they used to.
I'm wary that I still look at buying things as a bandaid to my problems, even though I try to play it out by shopping ethically instead. I suppose I should congratulate myself on how far I have progressed, too. We're constantly learning better.