Why Crying in dream

Hello guys Can someone tell me why this happens? This has been happening to me more often since today. Whenever I cry in my dreams due to some reason, my tears start falling in real. Meaning, whatever we see in our dreams, it must be an imaginary thing, so how can this crying become real and my eyes open up like this, still my tears fall on thinking about that thing, why does it happen And this happens only once or twice a year