I heard this in a sermon when I was a child and have remembered it ever since:
For every worry under the sun
There is a remedy or there is none
If there is one - seek till you find it
If there is none - then never mind it!
For some reason that has stuck with me and gives a bit of peace when I find my brain in a whirl. My dad was bipolar (manic-depressive back then) and I thought that little poem would cure him! That didn't work, but ... it has helped me over the years.