In every relationship there is a separation. Separation will happen, of course, this will be certain when you die. In most relationships, the separation happens before death. Especially if they are not married and just lovers.
If the person broke up with his lover of his own free will, he may not be upset after the separation. Because he has taken this decision before and the result of separation has been predicted.
Some people experience a great depression after separation. It takes years to get over this.