Like I said last week, publishing is a difficult business. And there will always come a time when you wonder whether you're wasting your time—whether you should even be writing at all.
How do you know when to keep going and when it's time to quit? Ultimately, only you can decide, but personally, I would first ask...
Do you enjoy it?
If you have time to write and you enjoy it—not getting published but the act of writing itself—then don't quit! Why would you? We only have a limited number of days on this Earth. You might as well spend them doing something you love.
But nothing is fun forever, so...
What if you don't enjoy it?
This is a harder question. If writing pays your bills, that's fantastic and maybe a good reason to do it. (MAYBE.) If it's not and you're just hoping to get rich, well... that's a bad idea, statistically speaking.
So, if writing doesn't bring you joy, and it's not sustaining your existence, then that begs a more difficult question....
Why are you writing?
Truth-telling time. I've been writing seriously for decades, but the last few years, I found an increasing fear every time I sat down to write. I enjoyed being done with something, but I only got that feeling once a year or something. I wasn't making money with my novels, and I had very low prospects of doing so.
All of that's par for the course, but I was also dreading the act of writing itself. The thought that I "had to" write every day was stressing me out.
It took me a lot of therapy and inner work to figure out that a large part of why I was writing was for external validation. I wanted people to read what I wrote and think I was cool—that I had worth. Turns out, that's not a great reason to write.
But I do love writing. My mind is spinning worlds and stories all the time, and I want them to go somewhere. I've done game design, D&D, novels, short stories, and I love them all! But novels are such a great medium for the stories I want to tell that I haven't been able to give them up yet. As I'm learning to let go of the need for validation (NOT! EASY!), my self-inflicted pressure to write has eased, and I've found myself enjoying the act of writing again.*
* Not always. It's still hard, but I'm motivated to work through it. Everything's a process.
Figure out why you're writing.
Your own motivation might be a mix of things, healthy and otherwise. And that's fine! Virtually all of our motivations are like that. But when writing or trying to get published becomes hard—and it will get hard!—understanding yourself is the only way you'll know whether it's worth it to you.
And fun fact! Even if you give up writing for a time, you can always come back to it. It's not like it's going anywhere, and you might learn a lot about yourself in the process.