When to Give Up: Never. Because "writing is a creative art and brings you joy." quoth Miss Snark.
In the same post, she also says, "You recognize that doing something difficult over and over again, and trying your utmost to improve is a worthy endeavor even if you fall short of your goal." In Zen, we say, Seven times fall down, eight times get up. This applies to martial arts as well, and pretty directly.
And, "The very act of writing is its own reward. It teaches you (if you pay attention) how to see the world through different eyes; how to wield language skilfully; how to organize a persuasive presentation." Just so, the path is the destination.
"Immersion in the life of the world, a willingness to be inhabited by and to speak for others, including those beyond the realm of the human, these are the practices not just of the bodhisattva but of the writer." --Jane Hirshfield