A few of the habits that I've found to be supportive of these goals:
:: Keeping a list of pieces that are enough and that serve me, my lifestyle at the moment, + my climate well. I revisit this list periodically + make changes based on recent observations. My current year-round, every-day-wear list looks like this:
:: Going through all of my pieces, trying them on + assessing needs at the beginning of each season. With the above list in hand, I figure out what I need to replace + focus on finding only those pieces. (Though I'm not super strict about excluding a perfect, fair gem that I can afford.) Then I can settle in + be content with the good things I have at the ready.
:: Letting things go periodically not only funds necessary purchases + keeps those pieces in use...but it also helps to hone my preferences + reminds me to choose wisely.
:: Being quite picky. When my pieces of clothing are few, each one needs to work hard.
:: Being willing to go without. At this point, I know that I can make do with few pieces of clothing.
:: Keeping a (not-too-long) list of my personal go-to thrift spots/sites, sewing resources + fair brands. I start my shopping search at my local thrift shops...then I'll take a look at ebay, etsy + poshmark. I'll consider making, and then I refer to the ethical brands list (scanning for my favorites).
:: Keeping a "desirables" list. Sometimes I come across something lovely for which I don't currently have the money or need. I'll make a note of it + know that I can revisit it, if I want to. Somehow just having this list allows me to obsess a little less about lovely things. I try to keep this list minimal + delete items about as often as I add them.
:: Reminding myself that I don't need to own all of the lovely things. Sometimes just curating a collection of lovely things is enough.
:: Limiting exposure. I try to be mindful of the shops I go into, the instagram accounts I'm following + the email lists to which I'm subscribed. Sometimes these things are just invitations to look + want. I want to want what I already have.
I've probably said all of this before, but since it's not a one time + done thing...a reminder is helpful at least for me. :)