Why are these groups often so great, so welcome, so precious?  Real life is very rich - theories only capture aspects of this richness.  However a theory, that I like a lot, highlights one reason why these peer groups are so important.  The theory is Self-Determination Theory (SDT).  It has evolved for over three decades.  The SDT website (see below) is a treasure trove of information about this approach.  It contains hundreds of research papers covering SDT's application to many fields including happiness, wellbeing, friendship, couples, parenting, education, psychotherapy, healthcare, political/ecological action - to name just some of the more obviously relevant. 

SDT focuses particularly on the crucial importance of satisfying three basic psychological needs - autonomy, competence and relatedness.  It proposes that:

Up, making time for a longer yoga practice this morning. Settle on Satie's piano music as a background CD. Sitting meditating with Catero. A plunge in the stream. Such a beautiful spring morning.