After a while you learn
the subtle difference between
holding a hand and chaining a soul,
and you learn that love doesn't mean possession
and company doesn't mean security.
And you begin to learn that kisses aren't contracts
and presents aren't promises,
And you begin to accept
your defeats with your head up and your eyes open
with the grace of an adult not the grief of a child.
And you learn to build your roads today
because tomorrow's ground is too uncertain for plans
and futures have ways of falling down in mid-flight.
After awhile you learn that even sunshine
burns if you get too much.
So plant your own garden and decorate your own soul
instead of waiting for someone to bring you flowers.
And you learn that you really can endure
that you really are strong
and you really do have worth
and you learn
and you learn...

(Veronica A. Shoffstall 1971)

I think it's the same when you lose a dear friendship and your heart aches. When you realize that nothing lasts forever, that people change (not always for the better), that some words can mean the world today and become empty of all meaning tomorrow, that life's decisions are tough, that the price for your personal progress may be a huge loneliness, that the best you can do is just...