The first of theteaches that suffering in life (Pa. dukkha) is inescapable. The Buddhist tradition distinguishes between three kinds of suffering: the first is biological (e.g. sickness, ageing, death), the second psychological (e.g. grief, misfortune), the third emotional (frustration, longing for someone).
Basically, all suffering is grounded in– of human existence as well as of all spiritual and physical pleasures. Everything changes; nothing remains the same. This is also why happiness is considered suffering, for happiness lasts but a moment in time, and will inevitably pass.