If you have no peace, nothing is right and life is unsettled.  Watch the animals, when nothing works for them, they curl up or stretch out and just surrender to the moment. Most widows, on the other hand, rest in a state of anxiety, guilt or unease.  This stops them from receiving the benefit of rest, which is to restore and heal.
  1.  Even grief, when accepted fearlessly, is restorative as we heal.  So rest when you need it, but really rest in mind and body.
  2.  Focus quietly on your loss, don't avoid or cover up your feelings.
  3.  Now think the word "relax". - Repeat 5x
  4.  When you have had a minute to relax - think the word "rest".
  5.  Say it to your broken heart.  Actual say to yourself, "I'm resting my broken heart."
It helps if you do this a few times daily before it kicks in.  The more you practice the simple intention to rest, the easier it will become for you to find peace in doing nothing, so that your body and heart can start to heal.