How would you feel or respond when someone gives you a broad smile? There's every possibility you would be happy and you could even smile back. Yes, that's the power of a smile. Sincere smiles from persons be it our friends or complete strangers always create good feelings inside us.

My neighbor Ruth once said:

My late husband, Samuel, had this warm smile and when we look at each other, I feel more relaxed and secure.

A genuine smile can tell a person how we feel on the inside. It signifies positive emotions like happiness, pleasure, laughter, amusement. Indeed The Webster's dictionary defines smile as "A pleasant or favorable disposition."
Newborns are said to "interpret facial expressions with great precision." Remarked an article in Observer, an online journal of the Association for Psychological Science. The same article stated: "Not only do people deduce useful information from smiles, they also use this knowledge to direct their own behaviour."

The genuine and sincere smile on the facial expression from caregivers and nurses can go a long way in improving the health of the elderly patients.

When caregivers' facial expressions are perceived as warm, caring, empathetic and concerned, the elderly patients would feel more satisfied and you would notice that their physical and mental well-being will improve. But if the opposite is the case, the caregivers nonverbal communications would distance them from the patients and might affect the patient negatively.
Studies had suggested that the benefit of smiling include increased confidence, reduced feelings of stress and happiness. On The other hand, when frown you may have the opposite effect.
When You smile you are doing yourself a very big favor.

Smile - Morale Booster

Smile does boost morale. Ruth, earlier mentioned, sometimes suffer from depression due to the untimely death of her husband.

She recalled,

Just seeing the smile of my mother, mother-in-law, sister and brother boosted my morale and strengthened my determination to endure.

When you see your family members, loved ones or those that are special to you smile or laugh out loud, it will fill you with intense joy and happiness, even if you are having a bad day.

But You may feel that life's troubles or anxieties may give you little reason for smiling. Also have it in mind that what you feel comes before your thought. That is why it is better, though it may be hard to always focus on the positive, good side of things whenever possible.

Also, you don't have to wait for others to smile at you. Take the initiative! Let it be at your own discretion. Try and add little happiness to someone else's day.
Make their day!
Smile increases face value.
See your smile for what it really is. A natural gift that refines and beautifies you and the persons who see it.