I have held a theory for a while that we are meant to function in a kind of honeycomb of mutual care. I say honey comb because they have hexagons.
If we are lone hexagons, we do not need to care for other people and can focus on caring for ourselves. There is some perceived personal safety in this, we do not need to risk "wasting love" on "unworthy" people. Also we do not need to risk opening up to anyone for them to hurt us and use information against us. This, while seemingly "safe" has a whole host of problems of it's own. What do you do when life goes pear shaped. How do you cope when things get to be too much. Shallow relationships with passers by do not satisfy our need for companionship and love.
However if we love and care for a few friends close to us, then they love and care for the people close to them, and so on, slowly the circle spreads. 6 is not a necessary number, it is just that hexagons fit nicely together. If you love and care for, for example, 6 people, and 6 people love and care for you, then you will have 6 times the love and care as you are giving and will find you are able to give more.
the problem with only loving and caring for 1 or 2 people is that if they can't or don't love and care for you, you can burn out. The trouble with loving and caring for 60 people is that you spread yourself too thin. This is not to say you ignore anyone other then the chosen few, just that your close circle can't be too big.
If one of your close friends is having a time of neediness, and can't love and care for you in return, having other friends who can care for you and share the burden is important.
This model, one that has been part of churches in the form of bible study care groups. Loving a few people in a lot of ways.