Expectations make us sad
Most of the time, we humans being trapped in illusions, start expecting a lot from people around us. When expectations do not take shape of reality, we are aggrieved. This is something that we keep on doing on a regular basis. When we see others doing this, we console them until our turn hasn't come. Once our turn comes, we choose exactly the same path and feel the same like others. This is something like a cyclic process. Most of us do not know how to avoid it, therefore we are unhappy and suffering.