Short answer: someone is always listening. It may not be the person you want or the person you think, but someone always has their eye on you and their ears turned forward, waiting attentively to see your next move, to see how you use your words, to see how you use the power (or lack thereof) that you have been bestowed. For whoever is looking and listening at the right time, just because you do not get to see the impact it might have on them does not mean it does not exist. I am a firm believer in the notion that, even though no one might be around when the tree falls in the forest, it doesn't mean that the effect was not felt indirectly. The rumble in the ground can stir the worms in the soil, can cause the plants to shrivel up, can cause the animals to relocate as they look for new sources of nourishment...You will not see or feel the effect of most of what you do on this planet, but it does not mean that it does not exist and is not actively interacting with you and the people around you on a daily basis.
All in all, be careful with your power. Speak your truth, but speak it kindly and with an open mind. Speak with the sensitivity of knowing that your greatest adversary and ally both might be watching, and with the intent of both of them emerging better than they were before. Be heard in whatever small way you can, even if it may seem fruitless.