My aunt once requested me to clean her house after she returned from abroad. On seeing layers of dust accumulated over the years, I realized it’s going to be a tough job to get everything spotlessly clean. I cleaned the ceiling, fans, showcases and chairs, and then I went over to clean what I thought was a flat wooden board. As I began to dust it off, I was astonished to see that it was a mirror—I could hardly see my reflection on it. As the dust came off from its surface, the reflected image took on better clarity. But there were hard stains on it that blocked a clear vision, so I rubbed harder with soap and water. Gradually the mirror appeared sparkling clean, and I saw my full image in the reflection. 
Lord Caitanya Mahaprabhu compares the mind to a dirty mirror and the chanting of the holy names to the cleaning process. Layers of dirt in the form of unwanted things lust, anger, greed, etc.have accumulated in our heart since time immemorial. Unable to see ourselves clearly, we misidentify with our body and bodily connections like family, nation, gender, and so on. Ceto darpana marjanam: the holy name of Krishna can clean the mirror of the heart and make it sparkle. All we need to do is call out to Krishna sincerely. We will soon realize our constitutional position as an eternal servant of Krishna in the spiritual world.