but keep the old. Great advice, and it can be applied to our work (find new contacts, maintain old resources), spirituality (be educated about other ways to nourish your soul, keep up with old traditions), and relationships.
As far as the last category goes, we obviously must nurture our connection with our spouse or partner. But making new friends can be one way of supporting that relationship, too. What I mean is that when we keep up with our friends and make new, non-couple friends for ourselves individually, we actually are helping that primary relationship by maintaining our own sense of self. No one wants to be the person so tightly bound in her marriage or enmeshed with her boyfriend, that she forgets who she is and no one really wants to be in a relationship with that person, either.
Book club, a running group, meeting a different friend for coffee each week these are small commitments to making yourself happier and more balanced. Keeping up outside interests challenges us, and helps us grow and change, and makes us more interesting when we do come back home.