We are meant to connect. There is a nerve bundle called the Vagus nerve and it fires when you see or experience connection. When it fires it releases a drug called oxcitocin, which is cleverly nicknamed the "love" hormone. Thus Science would say that we should feel happier if we seek to connect and cooperate.
Energetically we can use this in our practice since it really isn't the postures that are going to make us happier per say. They may make us happier in our bodies and relieve pain but it's the intention that we add to the practice that really makes for a great recipe. Say you practice for a specific friend, thus adding the magical ingredient of "love" or connection or meaning. Whoa meaning! love! connection!... I think my vagus nerve is firing... my chest is expanding and I'm feeling a little teary and excited. :)
Since it's also been Scientifically proven that the human race is connected then if you practice for someone else they will feel it and what a great gift to give a friend an energetic moment of pure love and specially delivered by universe.