We can control ourselves. Yes, falling in love with someone is a choice, because we choose who we hang out with. We also have control over our emotions. A person cannot let themselves think things if they do not like where those things will lead. Love is much less emotional than people today make it out to be.
The only reason one falls out of love is because the relationship is lacking in something or does not have a 'spark' to it. The spark is not love, love comes after the spark has faded and you feel a much deeper connection.
Most people do not understand this. Most people believe the spark is love and therefore forfeit their relationship. And many do not work as they should on the relationship.
One person or the both has to have done or not done something which resulted in the relationship ending. This creates the feelings you have. That us why honestly is key in a relationship. Because without it you're driving blindfolded.