I also kept a small journal (which I was very ashamed of!) when I was depressed, and like you I found that it was helpful as it was at least a small but very free outlet to express what would definitely be difficult to talk about.
And I've also recovered :) And like you too, I don't keep a journal so much now, in fact very rarely I'd write in it and come to think of it, it was usually when I was very grumpy that I turned to it.
So I can't help but be glad that I don't have much of a journal now. I also feel your conundrum with happy memories, but one thing depression has taught me is to count every "now" moment as a blessing. I've a goldfish memory but I'm very precious about remembering the good emotions, like happiness, peace etc, and that for me is enough. And enough to carry me forward and whack the occasional blues. And anyway, I always find that we inadvertently store memories, be it random phone captures, spontaneous scribbling, reminders of cringey moments by friends and family ... as corny as it sounds, we're all made of our past and we all love to share things. So no need for fomo!
Here's the repo for the abandoned project:
Last year I met someone more dear to my heart than I had ever imagined. Nearly every day since then has been of joyful bliss. However, I was enjoying myself so much that I stopped bothering to record my journals for months at a time. How ironic is it that in this time with so much meaning and so much happiness and shared experience to record, I felt that there was no need to record it, because I was having such a great time. Now I regret not having a reference for us to look back upon.
The article may not apply to everyone, but to me, it certainly does.