Hitting my head against the wall

Have you ever had a day when no matter how hard or many ways you try, you just can't get your point across? This happened today with my freshman. I spent all class period, 80 mins., trying to teach them this grammar concept. How many different ways can one teach a concept, I mean really? After modeling three different ways to figure out how to obtain the answer, I ran out of ideas. Here's hoping at least half of my 33 students understood today's lesson. Guess I'll find out tomorrow when we grade their work. You ever have a day like this?