In the olden days, if you wanted to submit an article to a magazine, you had to print it off, stuff it in an envelope, and put it in the post. You also had to enclose a stamped self-addressed envelope (licking the stamps). Then, if the magazine or journal didn’t want the fruits of your ambitious intellect, they could send them back to you. (Obviously, you’d then put the pages in another envelope and send them out again. Eventually, you might find someone amenable to publication.)
When your self-addressed envelope came crashing back on the mat, it would have a little rejection slip attached to it. Often, these were straightforward printed slips. “Not suitable at the moment.” “Not for us.” (They never mentioned who they thought it might be for.) Occasionally, the editor would add one or two thoughtful phrases remarking on what they thought were the piece’s strengths, and encourage you to submit further work.
You could use these slips as a bulwark for your determination. You could pin them to the notice board above your typewriter. You could glare at them while you pounded out the next piece. “I will make it.” “This piece will be published.” They certainly spurred me on. A rejection slip was only an invitation to send something else somewhere else.
Now, however, we submit our pieces electronically. The response — if there is a response at all — isn’t something you can pin on a notice board and glare at. The world’s trees are probably thankful for the demise of the rejection slip, but you’ll need to find something else that disciplines you to write, and to keep on writing. Kittens, maybe?