Companionate love does not have the fire and the heat that passionate love does, but it can more than compensate in the form of closeness, trust and affection. Furthermore it lasts much longer than passionate love, which subsides relatively quickly.

Another way of defining love is in terms of three components: passion, commitment and intimacy. These interact with one another in various combinations, so that no two relationships are alike.

Long-term satisfaction in relationships does not depend on material wealth or success. Nor does it depend on physical attractiveness. A recent study of middle-aged college graduates indicated that good-looking people, on average, were no more satisfied with their marriages or with their lives, than were plainer people.

So what does constitute long-term contentment in relationships? Psychologists have found that a feeling of equity is important. That is, the partners feel they are each getting about as much as they're giving. Not that they keep score, but over the long run things even out. This is similar to just being good friends to one another, supporting one another, laughing at each other's jokes even though you've heard them dozens of times. Another ingredient in long-term relationships is investment. This refers to material possessions, time and emotional investment. The greater the investment, the more likely the couple will stay together.

What does all this have to do with Valentine's Day? If you wish, buy that card or those flowers, but keep in mind that this is not a maker or breaker of a relationship. Better yet, show your partner love and consideration on the other 364 days in the year. It will make a greater impact than doing so according to the calendar.