Peace is a state of mind free of oppressive and unpleasant thoughts and emotions.
Having a peace of mind is the most healthiest thing on earth.
Without peace of mind, one find it difficult to make good decisions.
Absence of peace of mind affects one's entire life (mentally, physically, spiritually, emotionally and healthwise. That's why we need to embrace it, nurture it, cultivate it and develop it to suit our body and soul.
When you are downhearted:
Do breathing exercise(deep breath in and out).
Try taking a walk either alone or with a friend.
Meet people and listen to their own stories, encourage them, that way you will feel relieved by discovering your own challenge is not the worst.
Discover what you enjoy doing, for instance, dancing, listening to music, writing, drawing.
Appreciate yourself by discovering who you are no matter what you have been through.
Look at yourself at the mirror and say this to yourself "I'm beautiful, smart, brave and loving ".
Stay with people that's sees the best in you and appreciate your kind of person because such people that will never cease to put a smile on your face.
When people get you upset, let them know how you feel but in a polite manner not by being rude. Telling them your mind, aids in eliminating stress.
Let go of things that dosen't worth your happiness.
According to peace quarters.." being at peace is the ultimate position of power".
Learn to be at peace with yourself, that way, you will be at peace with everyone around you. 
Peace of mind is a decision you make for yourself not the situation you are in that being it. Nice work
Very good peace of mind