Sometime we are literally ask this question with ourself and stop ourselves to saying our heart talk which is very important to tell.

We stop ourselves for saying anything which is most of the time right thing to say at that point of time. We always stop ourselves for saying anything good but when it comes to wrong thing or bad words we don't even think twice and say immediately without even thinking that how other person feel and how much this effect him. Sometime our small word or sentence can give ake some strength to fight or to stand against their problem. Sometime saying something is need on that certain point of time. Because of we get or listen some positive or motivated words from others it really gave so much power. Sometime it does the work for antidote for so many disease. Because when someone don't feeling good or struggling with some life threatening disease they need someone who can sit with them or say some positive words and comfort him after saying some small sentence you don't always some long sentences to console them just need a smile and some lovely words to them. 

Sometime when something wrong activity happen with others we always stop us by saying that it is not our matter why should we have to something and even have fear that if they hurt also so.what can we do for this we even close our eyes and try to ignore all this wrong this which is very wrong and ask ourselves should I have to say something. This is the moment when we have to realise that which person is trapped in that situation just want you to say something because they can't say in that point of time and actually want you to stand with them and say some strong word to stop that person for doing wrong activities. Your small fear of not saying because that wrong doing person can also effect you can destroy that needy persons life.

Lastly I just wanna say that saying nonsense or long talk just say some small or strong word which can not only change others life but also can make good changes in your life or make you feel good and give you so much strength and power to develop In a good way. 

Always be happy and try to make others happy with your utter.