Below is an excerpt from John Irving's 1978 novel The World According to Garp:
Garp threw away his second novel and began a second novel. Unlike Alice, Garp was a real writer—not because he wrote more beautifully than she wrote but because he knew what every artist should know: as Garp put it, “You only grow by coming to the end of something and by beginning something else.” Even if these so-called endings and beginnings are illusions. Garp did not write faster than anyone else, or more; he simply always worked with the idea of completion in mind.
Finish what you start, or throw it away and start something you'll finish. Ship it.
On the other hand, you can put it aside and let it marinate. Everything comes to use, eventually. You can only connect the dots looking backward after the experience.