When we examine the workings of our words, we come to see that they, more than any other human capacity, define us. What we say and how we say it is who we are. Angry hurtful words define an angry hurtful person. Kind, considerate words define a kind, considerate person. This can be seen by considering the unique nature of the tongue: it is partially hidden and partly revealed. It is usually not seen, but it is heard. Maharal concludes that Hashem designed the tongue to reflect its function, which is to reveal the hidden self--one's thoughts, ideas and personality. The tongue takes these hidden elements from within the person and through words, brings them into the open.
The laws of proper speech are Hashem's specific practical directives for how to use this defining capacity. They teach us how to look at people, speak to people and speak about people. They reflect the Torah's wisdom which sees the impact and ripple effect of every negative interaction. The Torah understands that at the core of virtually every broken friendship, shattered career or divorce is a seed of hatred, a seed usually planted by a hurtful word. The Torah's laws reflect Hashem's knowledge that much of the pain and anguish of life can be averted by restraining ourselves from sowing these seeds. It is actually a simple principle: If one removes negativity, gossip, slander and divisiveness from one's vocabulary, one automatically and dramatically improves one's own life and the lives of everyone in one's environment.
(Artscroll Series, Chofets Chaim A Lesson A Day by Rabbi Shimon Finkelman, Rabbi Yitzchak Berkowitz.)
A sincere study of the laws of Shmirat Lashon will change your life, your relationships with others and particularly your relationship with Hashem.
A series of shiurim on the book quoted above entitled taught by Rabbi Beinish Ginsburg, can be downloaded part I, part II and part III.