It is hard to let things go. With sentimental things, the memories hold us back. With regular items, we see the use the item still has and the money we spent on it. The best advice here is to get passionate about a charity! It won’t help with the sentimental items unless that item is china, furniture or the like. But it will help with the useful stuff.
I haven’t met one person, friend or client; that feels good about just throwing something out. I feel it is in our nature to want to help, to reuse or repurpose. You may already have an organization that you help – get a complete list of items they will take. If you don’t, do some research about organizations and agencies and see what hits home. Find something that uses the goods or the money raised from selling the goods in a way you like.
Freecycle and Craigslist can be easy and fast ways to just gives things away for free to someone that just wants it. Salvation Army, Goodwill, Captain are some organizations that sell your items for programs. A further step is organizations that take certain types of things for certain programs, i.e. office products for unemployed to reenter the workforce (office attire is often part of this too like Dressed for Success), or kitchen and household items for domestic violence victims to restart their lives and old towels/sheets for humane societies.
If something has life and use left it in and you have some time, find something to donate to. It really will make the letting go process much easier and much more rewarding.