Peace & Calm
It is simply letting the Lord carry our burdens and manage our affairs for us, instead of trying to do it ourselves.
There are two things which are more utterly incompatible than even oil and water, and these two are trust and worry.
Let your souls lie down upon His sweet will, as your bodies lie down in your beds at night. Relax every strain and lay off every burden. Let yourselves go in perfect abandonment of ease and comfort, sure that when He holds you up you are perfectly safe.
Trust and worry cannot go together. If your work is a burden, it is because you are not trusting it to Him. But if you do trust it to Him, you will surely find that the yoke He puts upon you is easy, and the burden He gives you to carry is light.