My first piece of advice is stop thinking about whether it’s “decent” or not! Assessments of quality are stifling at the early stages of drafting in particular (and all throughout the writing process!)— just do the best you can at any given moment. And my second piece of advice is to stop worrying about getting anything “done”! All I did from ages 11-20 was write little broken pieces of stories that fizzled out after ten pages, twenty pages, fifty pages, three hundred pages…and then one day I found something that I thought was worth writing to the end. And after that I was able to finish things more often. But no time spent writing little pieces is ever wasted— Divergent was one of those pieces, for me, something I started and abandoned quickly after my freshman year of college and then picked up again four years later with a fresh perspective. I don’t really think any writing is wasted. Everything gets you where you need to go.
So, once you’ve stopped worrying about both of those things, try to just write because you love it. Write even when you don’t love it, too. And you’ll be fine.