I've been keeping a journal/s irregularly since I first could write, a couple of years when I was about 18-20 I kept three or four journals consistently, writing every day. Since then however I write whenever my head gets too full of events/feelings, and I need to write. It may sound strange, but I visualize my journals as though someone else were to read them, and I'm telling the story of my life, my walk with the Lord, my struggles, my joys, etc. So the things that don't matter so much (ie. day to day stuff) doesn't get included as much as major events, or things God is teaching me, or my relationship with others. I have three journals written in this way, and I have finished each one exactly a year from the day I started them. I'm working on my fourth one at the moment. They act as a summary of my year, and all the things I learnt and the ways I grew.
Unless I'm sharing specific parts of my journal with someone in order to encourage/help them, I don't share my personal writings with anyone. Maybe someday though, they'll all be read.
I don't write in it every day but I do make a point to do so a couple times each week.