Most of us have done the high street spree - buying tons of super cheap clothes that, for a brief period of time, make us feel good because we've got a shiny new wardrobe.
Some of us have been guilty of not even bothering to return ill-fitting clothes, because they are so cheap, it's not worth the effort.
To some of you, this is part and parcel of fast fashion. We buy it, it falls apart and we don't give it a second thought. But this cycle we are trapped in - excessive buying and discarding - is not just harming our planet.
Sustainable fashion is first and foremost about people.
To quote designer Tom Cridland who is dedicated to creating sustainable items of clothing that will last 30 years: "In places like China, India and Bangladesh the working conditions for those making the clothing we take for granted are horrendous and they can often not even afford basic living expenses."
A survivor from the Rana Plaza garment factory collapse in 2013
Put bluntly, our fast fashion decisions are often at the expense of people who don't have any choice. And after you read Rachel Moss's piece on why any self-respecting feminist (or human) should consider the impact their fashion buying is having on women in far harsher circumstances than their own, you may want to find out more.
That's why we've decided to focus on sustainable fashion for the month of September. We want to redefine modern consumerism - in other words, how and why we buy the clothes we wear.
Because honestly, how did we get to a point where we care so little about our clothes that we're willing to throw it in the bin because returning it is too much hassle?
To amplify the message, we've asked one of the most powerful voices in sustainable fashion to be our guest editor for this month: Livia Firth, the creative director of Eco Age.
Livia's dedication to the cause is unquestionable. Some of you might remember her Green Carpet challenge begun in 2010, when she would only wear re-purposed, upcycled or outfits made with innovative fibres (recycled plastic bottles to be one of them) at red carpet events to prove how it was possible to create stylish, sustainable fashion.
A particularly memorable outfit was re-purposing husband Colin's old suit for the Paris premiere of The King's Speech. (She looked fantastic, of course, see below).
More recently, she worked on documentary The True Cost, about the Rana Plaza factory collapse in 2013, where 1,134 workers died in a Bangladeshi garment factory.
Harking back to that powerful message that sustainable fashion is about people, she said: "We must respect these workers as we do our children; our friends. They are no different to us."
She'll be revealing, on 18 September, why she feels so passionately about this subject, as well as curating a special selection of features on the day.
We'll also be talking to designer and eco warrior Zandra Rhodes, who will be opening London Fashion Week, as well as interviewing Tom about his new project, the 30 year t-shirt.
Of course, in true HuffPost style, we won't shy away from some truth-telling.
Most of us buy fast fashion because let's face it, it's cheaper. But truthfully, it isn't actually cheaper because it falls apart much faster, which means you need to replace it more frequently.
So this is the perfect arena to discuss and share brands who are making affordable clothing that may be stylish, functional or both. Because believe us, they are out there.