My sister and I have children the same ages. One day (when they were small) I called her and told her what my kids were doing to drive me nuts.

[caption id="attachment_1030" align="aligncenter" width="331" caption="Matthew and his cousin Joshua. In most of the photos of Josh as a boy, he has a bruise on his face."]<a href="http://motherhoodstress.com/wp-content/uploads/2012/01/JoshMatt1983.jpg"><img class="size-full wp-image-1030" title="JoshMatt1983" src="http://motherhoodstress.com/wp-content/uploads/2012/01/JoshMatt1983.jpg" alt="" width="331" height="405" /></a>[/caption]

She laughed and said, "How childish of them!" And I laughed too.
That became a joke between us.  She'd call me, all stressed-out from some crazy thing her kids had done, and I'd tell her that her children were being SO childish.
That one phrase reminded us that they were, after all, just children.
And when one of us said, "How childish!" we would both laugh.