Why is it once you start crying you can't stop?

I'm sure it has something to do with once they've pulled that heart string they don't let go.
I saw it today,never read the book and really have no background on it besides this and another thread.
So anyway,I'm not sure what era this was suppose to be filmed in but I'm assuming 80's cause it had that feel as well and the film it was shot in.
The opening credits were pretty cool and still left me a bit confused as to what to expect. This turned out to be such a darling film. Nothing was over the top and that little boy looks just like Michael J. Fox,when MJF was a little chunky.

recious:Such a great story of friendship and child hood innocence.