Love Can Happen Multiple Times

The myth says every marriage is decided in heaven. If it is so, why do we love another person first? When God already knows, why does He let us love someone else, when He knows that it is going to be a disaster? He would like to play with our life to have fun. I am one of his victims; he made me love one girl, but my fate had different plans. Some people say love can only happen once, but I don't think it ends with one; it moves from one to the other. Yes! I'm serious; it happened to me.