Unsubscribe & unfollow
If you really want to stop with fast fashion, then start by unsubscribing from all your fashion brand newsletters.
Fashion brands that constantly launch new products or offer their clothes at discounts after only a few weeks may only be sustainable in name. Constantly sending emails to keep in touch with you to buy and buy and buy is not sustainable - it's just fast fashion in a new dress.
The same is true for influencers and brands on social platforms like Instagram. You are a member of shopping bargain portals? Unsubscribe there as well.