I've adopted a simple, straightforward rule for how to manage the material items in my life. When I acquire something new, something else goes out.
In general, that means an item is replaced by a similar item. I buy a new book, and another book gets donated. I download a new app, and at least one new app gets deleted. The same holds true for me with clothes, for example. I buy a new shirt, and at least one older shirt gets donated.
It's not a hard and fast rule. I'm not mindlessly discarding items simply for the sake of doing so. Yet this rule always factors into my thought process.
So, at the very least, I'm ever mindful about individual material items in my life and what comes, goes, and stays. Therefore, as I consider clothes, books, and other items in my life, I ask: Do I still wear (use) it? Will I wear (use) it in the future? Does the item have any meaning for me? Will I miss it if it's no longer in my life? Anything short of a "no" response to these questions means I keep the item. My responses may change in the future, and that's fine. But for now, I'm clear about my next step and don't need to perseverate over that individual item.