I'm a recovering hoarder (father and one sister are worse than me though). I started to get over it thanks to Marie Kondo's book "The Life-Changing Magic of Tidying Up: The Japanese Art of Decluttering and Organizing" (aka the KonMari Method). Hold every item and ask if it brings you joy. If not, then thank it for its service and donate or trash it.
So far I've made it through the clothing section and gotten rid of about 3/4 of my wardrobe.
Working on selling off many books from my humongous collection. Keeping only the RPGs I definitely want to play again, my WW2 photo histories and the fantasy novels I reread regularly.
Paperwork shouldn't be a problem except for my wife not having time to sit with me and go through what she needs to keep, though my personal rule of thumb is anything over three years old is "shred"