One of the hardest things about organizing is throwing and giving away your belongings. We form emotional attachments to our things. This is why it is really beneficial to have an unattached third party who can help us sort through our emotions to decide what is essential to keep.
But until I come help you make decisions about your items, here's a trick that can show you what you need and what you don't.
First, turn all of your hangers "backwards" like this:
Then, as you use an item, put it back in your closet the "normal" way you usually hang your clothes.
After 6 months to 1 year, donate or discard the clothes that are still on "backward" hangers. You can exclude seasonal and special event items from this rule, however. This is a clear cut way to see visually what clothes you have stopped wearing so you can create more space in your closet!