If you are having a bad day with your writing, the words won’t come and every page is painstakingly hard, it’s very easy to be tempted to discard your work, but resist that compulsion and simply put your writing away for another day. On a bad day, your perception of the standard may well be tainted and you will be particularly hard on yourself.
On another day when reviewing that material, you may be pleasantly surprised by how good your work actually is. Plus, as you had a reason for writing that material previously why not make use of the content? Re-write it, edit it or simply use snippets from it, and see how you feel on a day when the creative process is flying. Remember- no writing is ever wasted.