I started out, like many people, writing poetry. It wasn't just because the poetic form allowed me unfettered expression for my young, wallowing angst - although that was part of the reason. I also wanted to work in a format in which each word was a crucial part of the whole. I eventually graduated to stories, and then to a novel, currently under construction. Each of those transitions set me back in a steep learning curve. Storytelling media don't necessarily scale up.
Ken Liu sums up the challenges of moving between prose formats in this piece on Space.com: Writing Sci-Fi? First Understand How Elephants Aren't Dragonflies. Just as you can't scale up an arthropod to truck size (despite the insistence of hundreds of science fiction films), you can't just take the components you use to build a short story, hit them with the Grow-Ray, and expand them into a book.