I find this helpful tip from 101 Motivational tips free E-book from White Dove Books founded by Will Edwards his website is at www.whitedovebooks.co.uk/blog/
Tip #3 - Create a worry box.
Nothing is more aggravating than trying to work productively and
being nagged to death by worries! Instead of letting your worries
take over your mind, create a worry box to keep them in. You can
use any kind of box, from an empty shoe box to a decorative
wooden or glass box. Write all of your current worries on a sheet
of paper (or you can use a fresh sheet for each worry). When you
can’t think of any other worries, put the sheet(s) of paper into the
box, close it and store it away on a high shelf nearby. If worries
begin to nag at you again while you’re trying to stay focused,
glance at your worry box and remind yourself that you don’t have
to worry about anything right now because you’ve placed your
worries in that box. Affirm that you can pick up your worries
again later if you really want to.