Has anyone read "The Life Changing Magic of Tidying Up" by Marie Kondo? It's really helpful in learning how to organize your house. A brief summary: start with clothes, then books, then papers, then personal items, then mementos. (From easy to more difficult.) And don't organize by room, but by subject, so that you take everything out of its place and examine one item at a time, while the group of items is all out in front of you. This way you can see at a glance what you have (usually a lot!), and eliminate one thing at a time. This is important because she advises that you assess for yourself whether each item sparks joy in you -- that is the one and only determining factor on whether or not to keep the item.
This cuts through all the excuses. "Oh but when I'm thinner maybe I can wear that again... or my sister bought me this so I can't throw it away." The idea is that the item has served its purpose -- either in the past, or if it's a gift, then the gift was a symbol of love and thoughtfulness that we can be grateful for, and then let it go. If you don't think too much about it, or give yourself time to come up with an excuse on why you are keeping the item, then you can assess how you feel about it intuitively. If you clear things out this way, in theory, you'll be surrounded only by things that give you joy!
I'm on a mission to sort through my household of stuff using this method over this next year. Maybe I'll do a little each month. Just cleaning out all the paperwork in my office took about 3 days over the holidays.