1. take photos. Once you take pictures, you don't have to worry about forgetting the memories. If you have a lot of letters or journals, try typing them out. It may seem overwhelming, but it doesn't take long when you do it in spurts. Now you can safely toss.
2. chunk it all. More of an extreme option, but probably the simplest. It’s good to just let go sometimes, especially if you have an overwhelming amount of stuff.
3. re-use or give away. It’s easier for me to part with something if I know somebody else will benefit from it. If you don't want to give it away, you can always try to find a use for it.
I used a combination of all three tips, but we're all different. Some people can throw everything out, while others can’t bring themselves to part with anything. How do you deal with stuff that holds sentimental value?