Falling in love, being in love - it's about the most threatening thing in the world. Making oneself completely open and vulnerable to another human being is the riskiest thing in the world. Wars have started because of love unrequited or gone awry. Love is about the most dangerous thing in the world. That's why I don't think it's schmaltzy. The real thing is a test of our strength; being able not only to feel this way, but to mean it - it entails the greatest threat and possibility of being fully human there is.
In the context in which this comment was made - responding to my sister's claim that a certain song was "schmaltz", I think it is important to amplify this statement a bit. We, especially Americans, love love. That is to say, we are a hopelessly romantic people. We think there is something all warm and cozy about love. We do not fear it, but desire it above all other states.
There is much to recommend being in love. There are few states as filled with moments of wonder and rapture. Yet, if we were honest, we would also admit there are few states as dangerous to our very selves as being in love. To be in love, to really love another, one must first be willing, against all good sense, allow ourselves to be completely open, honest, and vulnerable with another human being as possible. Love is fraught with hazards, to which the phrase "broken heart" hardly does justice. People have been psychically destroyed by the end of a love affair. The betrayal of a loved one is far worse than any other emotional pain. It can leave a person worse than depressed; despair, destitution, violation - these and far more can result from a love betrayed, or even just collapsing.
I think remarking that a song expressing undying love is "schmaltzy" while it may be true, also is a kind of defensive ignorance. We are refusing to acknowledge the other side of such a declaration. Giving voice to such feelings runs the risk not only that they will be belittled; it also runs the risk that such openness will be rewarded with rejection, whether in the present or the future. Loving, like all of life, is a risk. It is the most dangerous risk we run. Love can bring life, it is true. Love that ends, however, that is betrayed, denied, or simply withers away over time, can destroy.