Sometimes in teaching, we come to a lesson, or perhaps even one or two problems that no matter how we try to explain the problem, our students can not grasp the idea. This can be especially hard to accept as a teacher. Sometimes you just need to slow down and walk away from a lesson for awhile. Teach it after lunch, or perhaps in the next day or two. Give the information you taught some time to sink in. If you feel frustrated, it's likely the students are frustrated as well. This can be especially hard for me, since I am so stubborn, but it is an important choice.
We write up this amazing lesson plan, teach it, and expect our children to grasp the concept. However, what seems easy and makes sense in our minds; isn't always the case with our students who are just being introduced to the subject. Be patient, slow down, and if necessary, wait a day or two.