When an arrow strikes you, you feel pain.
If a second arrow comes and strikes you in the same spot, the pain will be ten times worse.
The Buddha advised that when you have some pain in your body or your mind, breathe in and out and recognize the significance of that pain but don't exaggerate its importance.
If you stop to worry, to be fearful, to protest, to be angry about the pain, then you magnify the pain ten times or more.
Your worry is the second arrow.
You should protect yourself and not allow the second arrow to come, because the second arrow comes from you."
THICH NHAT HANH