This human realm is in an important sense the most fortunate station of rebirth. It is just here that the most favourable conditions for liberation are to be found. The lower realms are overwhelmed by suffering, and in the higher realms the pleasure is so constant that there is little incentive to practice. It is right here that the right mixture of pain and pleasure can be found.
We should reflect on the rare good fortune of a human birth, especially if we have a birth in a healthy body with sufficient intelligence to hear and understand the Dhamma, and the good karma to encounter the teachings. When we consider all the other terrible possibilities on the wheel, we would be foolish to squander so rare an opportunity.
It is said that the bare minimum requirement for taking a human rebirth is to keep the five moral precepts reasonably well. This is because to break a precept is to experience the consciousness of a lower realm. To perform an act of violence is to engage in the mind of a demon and foster rebirth in hell. To consume intoxicants is to lower one's mind to an animal level and to set the conditions for rebirth at that level.
This points to another characteristic of the human state. It may be said to be the realm in the middle of all the others. This means that a human can experience moments of consciousness equivalent to those of beings in other realms. Someone enjoying a refined sensuality, such as listening to a Bach fugue, may be touching on the mind of a deva. Likewise, absorption in meditation (jhana) is the equivalent of Brahma realm consciousness.