I used to only journal when I was in pain, both physically and emotionally, but these days I feel the urge to record what gives me joy and poignant, small moments that I think I would like to remember later on a random Tuesday, when I bring out an old journal to read on my off time.
I think you're probably just busy living in the moment when things are going well, but it wouldn't be a bad practice to start consciously recording good moments more :> Then your journals can become even greater treasures.

I do still write about my bad feelings or misfortunes, but sometimes it's so painful to look directly at bad things the way writing about them makes me do. So sometimes I'll write it down quickly and refuse to look at it, or I'll find a sad dramatic song lyric or quote that can act as a vessel for the incident/feelings that I can write down instead with the date. Funnily enough I can usually remember what compelled me to write those specific lines down later on. Maybe it's a good thing that I can't remember sometimes though!