I love the title as well as the idea of poems piling up. I also enjoyed the rhymes as they flowed really well.

"I forgot how quickly time would pass,
just seconds per each line."

Great opening. It's easily relatable and so true; time seems to pass so quickly when writing a poem. I think you could drop out either per or each since they are synonymous.

The second stanza is my favorite. It reminds me of how my sleepless nights would end up leaving me with unfinished poems. It's like you wrote it for me lol!

Great ending too. It brings the reader back to how these 'inspirations' leading to a lot of poems written, but we see the conflict from the poet, that although it is cathartic, those poems would end up being mere reminders of awful feelings the persona is feeling whilst writing them. It's sad but this is beautiful, Saffie. Thanks for sharing! Keep writing.

I forgot how quickly time would pass,
just seconds per each line.
And in the end was one more poem,
a poem to call mine.

^^
Perfect opening!
Just a few suggestions:
Keeping with Xanthe's suggestion of removing 'per' or each' - Personally, I don't think either should be removed, but perhaps change 'per' to 'for' ?? Your choice.
Also, the last line is slightly out of sync with the flow - perhaps try 'a poem to call all/just mine' ?? Again, your choice.

Sleepless nights, so many thoughts,
the books began to pile.
I only wish that all these books
were ones to make you smile.

^^
This stanza, by it self, is so relatable!

'sleepless nights, so many thoughts,
the books began to pile'

I can definitely relate to those two lines - now I tend to type them though I'd love to print them all in a book for each year of poems I have written.
And it's true, not all our thoughts or memories are pleasant and many of our poems (or mine at least) are filled with sorrow because it is an emotion that is easier for us to write about and one we find ourselves needing to release.

But all these poems are dark and deep,
filled with torture and pain.
And tonight here I am
Adding to that pile again.

^^
A perfect ending.
Personally, I don't imagine a stack of afore-mentioned books but rather tilting piles of paper filled with the words of your thoughts.

Overall;
Besides the couple of suggestions at the beginning, this piece is absolutely flawless!
So many poets would be able to relate to this piece.

However, though you have written it as though this 'poetry pile' is one of sadness, I don't think this poem belongs in the 'sadness and depression' folder. Perhaps 'life..' or 'miscellaneous' - I don't know, I just wouldn't have put it here.

Your title;
I love this! It's simple, yet speaks volumes. Perfect!

Another brilliant write. 5/5