I burn them. Usually my journals are tied to a certain phase in my life, and when I need to move on from that phase, I don't want any loose ends. I'm afraid people may read them that I don't want to read them.
I also use fire, or other forms of destruction (could be shredding for instance) to achieve closure.
When I divorced, I had to give up my house. I loved that house and its country location, so quiet, so full of birds and other wildlife. I mourned in advance of my moving out, and one ritual I performed was to burn my journals from the years I lived there.
I also recommend fire for closure from other things - for instance, love letters from an ex. There is something cleansing about it.
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A finger in every pie.