Completely get that. I often wonder about those prolific professional songwriter folks, who can write even several songs a single day. And sometimes they are DAMN good ones too.
I think this writing thing is a muscle, at least in my time doing this, over say about 30 years, I've written maybe 50 complete songs, mostly in spurts of three or four over a month or two.
Kind of depends where the family is, or what I've been doing as a career at the time. Sometimes long droughts between songs.
While I had two kids over eighteen years, I think I wrote three or four only, squandered a LOT of great "life story" opportunities but I just had no time, or inclination.
But I can tell I am getting slightly better at it with each few I finish, and it gets a little easier too. You learn how to just focus like crazy and pull it out of yourself. That's the hardest part.
Years ago, I would come up against a block, and put the guitar down and go do other things. Four months later I'd realize i have another half-written song I don't care to complete anymore. It's lost.
You have to strike while the inspiration is HOT, and don't give up. At least that's me anyway. Spit it out, get it on paper even if it's bad. You can totally fine tune it later. Often it's better when you do.
I think it's kind of like painting. You have to do it, over and over and over to get good at it, for more satisfying results.