In Buddhism, life can be defined as suffering. And the reason human beings suffer is because of what we desire, which at least some of the time, if not all of the time, we cannot fulfill. We might desire, for example, to be rich, but we never become rich. We can become obsessed not on what we have, but on what we do not have. This is a type of suffering. The longer we remain fixed on these things we cannot have, the deeper our suffering can become.