You cannot rest when you have to do something which you cannot. And you cannot rest when you feel you have to be someone whom you are not. You are not required to do what you cannot. You will not be asked to give what you cannot give. Nothing is expected of you that you cannot do. Doing service involves only doing what you can do. And no one wants you to be someone whom you are not.
This realization brings you deep rest. You cannot rest if you have either ambition or lethargy. Both are opposed to good rest. A lazy person will toss and turn at night and be "rest-less" and an ambitious person will burn inside. This rest brings up your talents and abilities and brings you closer to your nature. Even a slight feeling that the Divine is with you brings deep rest. And prayer, love and meditation are all flavors of deep rest.