Think a little before speak...We speak our words to reach each other and our way of speaking is much more important then whats we gonna speak to anyone. often we have noticed when we have a light mood then we say anything without thinking about it and later regret it.
It is necessary to remember by us before speaking to any person that the spoken word is not going to come back and its effect on the other person is also depends how do you speak and at the same time how did it feel by the other one. Even a bad person who know how to speak will win the other hearts and a nice person who never keeps any bad feeling for anyone and always wants others happiness, may do not have talent to speak would lose many things.
What we said is show our thinking so it is very important to keep positive thinking in our mind first that will help us to speak in a positive way whether the thing which we said is negative but still it sounds positive by the listener.