We all face challenges in our lives. It is how we deal with them that shows our mettle! Write about one of the hardest things with which you had to deal. It could be from your far distant past or something as immediate as five minutes ago. No need delving into any “True Confession” here. It was difficult and you survived it!
Alternatively, write a “hard” poem. Rocks, boulders, bricks and blocks are all hard. A stubborn person is considered “hard headed.” Backing away from a poetic prompt is hard if you try to do it every day (or every other day! 😉 ) Making a sudden turn is called a “hard left” (or right, depending on your persuasion!) So write that instead.