When a relationship begins, we usually feel passion and chemistry, pleasant nervousness and anticipation - the emotions most characteristic of early love. After years of love, these feelings subside and many couples face the question: are they really happy in their relationship, or are they just satisfied with the comfort that a long-term relationship brings? We asked what the experts think about it: how do you know if you still want a partner, or if you've just come to terms with the relationship?