So, I did go to a thrift store recently. Remember, while I gave them up for Lent, I didn't swear never to enter one again. Rather, I had planned to shop there mindfully. I really like using thrift stores--I'd much rather re-use something already created than buy something new. Such a waste to buy new again and again when there are perfectly good things already in existence.
I went in with a plan, with two items on my list: dressy pants and Daring To Dream by Nora Roberts. I found two pair of dressy pants (had to try on two dozen!) and I actually found the exact book I was looking for! I left happy, and having saved a lot over buying new.
Mindfullness is key. I didn't shop for entertainment, or just as a habit. I had a plan, I went in with a list, and I came out with exactly what I wanted.