I feel that the easiest way to avoid bragging is pretending my FB friends are in the room...would I show them/tell them what I am about to post? My FB friends are mostly RL friends and neighbors and relatives. Sure, a few second cousins and high school buddies I haven't seen in 20 years have requested to friend me, and I have accepted, but if they don't want to be updated with the random details of my life, they should hide or unfriend me!
So I post 3-5 pictures from any adult vacation, but not 100. And maybe 1-2 anecdotes. Maybe 10 pictures of a family vacation. One picture/comment if we do something cool locally like a restaurant/concert. More pictures and a short synopsis of an event like a birthday party. I post any cool thing I make, like my kids' birthday cakes and my daughter's dress for back to school. I post pictures and quotes of my kids (I sometimes wonder if I put too many of these, but then I get relatives and friends commenting that they love reading the quotes and seeing the pictures, so I keep it up at their request). If I ever posted something that gets no likes and no comments, I would look at that content and don't post something like it again...but I don't remember that ever happening.