Love and Marriage

During our reading of the novel, we've talked about good matches and good marriages. There are very few examples of a successful, happy marriage so far. The first one that comes to mind is the Count and Countess Rostov. Other than that, we have the Bergs and Boris and Julie. More often than not, Tolstoy shows us an example of an unhappy match, whether it be financial or emotional unhappiness. Andrew didn't love Lise, Pierre doesn't love Helene (although he thought he did at one point), and things don't look good for Andrew and Natasha. What is Tolstoy trying to say with this? Does he believe that the vast majority of marriages are unsuccessful? Is marrying for love (or lust) a bad idea? Would it be better for characters to marry for money, and try to be a good team rather than our idea of a good couple?