This saying is true. It is really hard for us to serve two people at the same time. God created us, people who only have one body, one brain, and most especially, one heart.
Loving two persons at the same time is like serving two people in one time. It is really complicated. Some people fall in love with another person even if they are already committed. Some will say that they are searching for something missing in their present love life and the other person fills it out. And as we all know, this is not right. But, what is the best thing to do in the situation like this? These are some of the things I think you should do:
You should think hard and decide who between the two of them is the one you really love. You would get to the point that you would say that they're just equal, but that is impossible; think again. Maybe the other one is the one you really love but you just don't know it right now. Just wait for the right time and you will discover it. You cannot love both of them. You SHOULD REALLY CHOOSE ONE. Also know if those people love you back or if they know that you love another person rather than just him/her.
In loving two people at the same time, others may consider you two-timer. They might get mad at you and hate you so you really need to do something about it. Take your time. Always think twice before doing something. Remember this, loving is a great thing only if it is in the right time and the right person.