When I like something, my instinct is to try to capture it and own it for myself. Pretty things are Pokemon and I gotta catch 'em all.
This is what led me to buy a DVD of every movie I'd ever enjoyed watching, even if I didn't plan to watch it again in the near future. Or buy copies of books I'd previously enjoyed reading, even though I rarely re-read books. Or buy clothes that don't look good on me, but look great on the model or the mannequin or the hanger. Buying and owning was a way of paying homage to things I love, of voting for them, of hitting the vast "like" button of commerce.
I use the past tense because I've mostly gotten over this (I think) (I hope). Okay, my behavior doesn't always reflect it, but intellectually, I've learned that:
You can like something without owning it.
Ownership is neither necessary nor sufficient for expressing appreciation and love for something. You can just... love it.
Here are some tactics for expressing admiration without acquiring.
This is ideal for the "dress looks great on the rack" scenario. Take a picture right in the store--it's free. Or pin the image to a Pinterest that is just for things you admire (warning: keep it separate from any Pinteresting you do for things you actually plan to buy).
All this said, I find myself genuinely uninterested in buying wrong-for-me clothes now that I've defined my true colors; I no longer feel the need to buy or own anything that I know won't work for me, no matter how great it is in theory or on someone else.
Similar to the Pinterest strategy above, but ideal for books and movies: keep a list of the ones you've experienced. I had basically been using my book and movie collections as physical representations of the books and movies I liked, but I could just as easily have used a list--it would have been cheaper and taken up less space! I think the feeling that I had to own every book as proof I'd read/liked it is a lot of what kept me from taking advantage of the great deal that is the library.
Now my book strategy is to get everything I can out of the library, and I write up a review on Goodreads when I'm done. This means I keep a record of what I've read, and it's even more valuable than the physical record of a book collection, because it allows me to preserve and revisit my thoughts and feelings on each book.
Writing and drawing have been great ways for me to admire things without owning them myself. I love the way Converse hi-tops look, but I find them uncomfortable to wear. For years I just drew characters in my comics wearing similar shoes. This allowed me to have those cool feelings about them without actually wearing them myself. Curating a stable of fictional people allowed me to use products to represent different traits about them without necessarily needing my own self to participate in that.
I have since bought and worn them, but honestly, I get more joy out of drawing them than wearing them.
This is an ideal strategy for items you use in a group setting, like board games. I've bought several games because I'd enjoyed them playing with friends, even though I really only ever play board games with those same friends, and our group really doesn't need more than one copy of any given game. My dollars would have been better spent buying any other game, in fact.
If you are generous with your own things, and cultivate a norm of mutual trading/borrowing/enjoying-together among your friends, each individual or family can own a subset of items, while reaping the benefits of many more. Anyway, that's the theory. It's a nice one, isn't it? I find it hard sometimes to actually put it into action, given that it requires social skills that being raised by the Internet has not prepared me for. I'm working on this.
Recognize that the best things in life are unownable
There's no way to own a sunset, or love, or a puppy dog's smile, etc. Of course, you can buy proxies for those things, but it's not really the same at all. A picture of a sunset, for example, can be bought, but it is in no way the same thing as really seeing one in person. Still, this is what I fall prey to most often these days, I think.
I love walking in the woods, so I'll buy new shoes for walking in the woods (never mind that my regular shoes are fine given the amount of woods-walking I actually do).
I love the light feeling you get when you're dangling your feet over a dock in summertime; let's buy a navy-and-cream nautical colors shirt I saw a girl wearing in an ad while dangling her feet over a dock in summertime, or that I could imagine wearing while dangling my feet over a dock in summertime.
It takes some skill to realize that the true essence of what you're trying to buy is not something that any product can capture. I'm working on this, too.