No human knew how to express their feelings becuase of an accidental curse.
Cupid is the son of venus, who was the god of love and beauty but did nothing about the curse.
Mother, I have to do something....
He was tired of all the hatred so he asked Zeus to become the god of love
Please help me...
Fine... you are now the new god of love
From then on Cupid helped people fall in love and peace people's hearts together, but cupid forgets who he already had hit with an arrow so sometimes the relationship doesn't work out and they fall out of love.