This is very important. You want your buyers to visualize themselves live in your house, not you living in it. Personal artifacts distract so you have to put them away – photographs, souvenirs, trophies, medals and certificates, posters, religious items, and family heirlooms.
If you’re a collector, then pack away your collectibles and valuables. Don’t forget your refrigerator’s door as it is one of the most common place to hang cute magnets, memos, postcards and all sorts of personal stuff.
The other reason to de-personalize has to do with safety. Buyers rummaging through your house are strangers and it would be better if they don’t know who lives there, or have access to any other personal data.