Educate the bullies
Want to avoid a double chin? Stop looking down all the time and turn your face up to the sky! You can't see anything when your head is down, but you can see everything when it's pointed up. While you're at it, put a smile on that face and it illuminates the path even more.
A forced smile is better than none, so don't get discouraged. After a while, it will be voluntary because smiling will inhale another smile, and another, and another. It's like a domino effect. After you've been doing it, you will feel that not so pleasant emotion of whatever it was that was making you feel so bad, so angry, so hurt, disintegrate into a happy, grateful, feeling that the Holy Spirit had been wanting to place into your heart for so long.
We are the ones who choose sadness or happiness. Strength or defeat. Worry or surrender. Smiling, can help you achieve all positivity. It radiates you from the inside and makes it swell to the point of bursting outside of your body, so that people can see and feel your light.
To me, that is what the Third Person of the Trinity, the Holy Spirit, is. All joy, all love, all peace. Simply saying, "Come Holy Spirit", is the spark you need. Like hitting a rock against another to start that fire.
So whether or not you "feel" like smiling, just give it a try. If it is not immediate, don't get discouraged. Keep going. The spark will ignite into a full flaming bonfire in your Soul and you won't even care if anyone smiles back. But I can assure you, they will remember it at some part of their day and realize that that kind of medicine is just what they needed to mend their broken Heart.
So smile!