I had a massive clear out recently, shredded old love letters from DH (yes he was standing right next to me when I did it) mainly because some of them were a bit racy
and it wasn't something I wanted my children to read if I died. They are my children, not my friends, I wouldn't choose to reveal certain information about my life with them.
We also shredded old blurred photos from before the age of digital technology when you just used to pray you got a good photo and then somehow end up keeping them no matter how bad they were.
I have kept some stuff, but I have kept them for me, not as something to be passed on or kept for generations.
My incredible, funny, amazing Mum died in 2010. She had started to fill in a book called From me to You, where they fill in information about the past. Sadly she died a mere 10 weeks after being diagnosed with cancer, she had no symptoms. Picked up on a routine mammogram.
I wish I had filmed her talking about the stuff I remember, when she found out she was pregnant with me, my birth story, her story of how she met my Dad, stuff from her childhood. I wouldn't want to read her diary though. Diaries are personal to the one who wrote it, not to be read by others.
I am under strict instructions that when my best friend dies I am to get rid of a certain box in her house with all her memorabilia in 
I would say get rid of stuff that makes you sad, no point keeping it. Keep only stuff that makes you happy or laugh.