What am I?

I can bring sadness or joy, cause a smile or a frown,
Inspire or depress, lift up or knock down.

I can stop tears from flowing or cause them to rush,
Spread warmth or freeze, encourage or crush.

I can hurt or heal, enlighten or obscure.
Make matters worse or deliver a cure.

I can open locked doors or slam them tight shut,
Close an old wound or open a cut.

I can make you laugh till you cry or bring you despair,
Harm you and break or protect and repair.

I can entertain with flair and keep you in awe,
Inspire and inform or tire and bore.

I can be serious and weighty or a bit of a tease,
Cause pain and distress or brighten and please.

I can cause wars to erupt or peace to ensue,
Quash faith and hope or foster it anew.

I can awaken the past or reach for tomorrow,
Shape destiny and history or plunge into sorrow.

I am words.