Why do people "fall out of love"?

yes. it has happened to me several times. The first time, with my first love, I thought it was it,but I quickly found out we had other interests. Later, my first marriage ended in divorce simply because I was too young, too emotionally immature and had wondering eyes. She was to busy with our two sons to pay any attention to me, so I thought, so I fell in love with other ladies....for a while it seemed like a different one each night.