I think, for me, learning to purge came down to learning to distinguish between items "loved" items and items I love now. It's very easy to look at something you haven't worn in a long time and conflate the thought, "Oh, I loved this five years ago!" with "Oh, I love this!" As with human relationships, sometimes the magic isn't there anymore, no matter how hard you try, and it's time to move on... It's an honesty thing. Just tell your sweaters, "It's not you, it's me. And don't worry, the right person for you is out there somewhere, just waiting for you to show up at the Goodwill."