thankyou so much for such a useful piece of advices
If you feel you are doing this on purpose, then you should seek help to determine if you have some pent up anger that you are taking out on others. Therapy is very beneficial in dealing with anger issues.
Not quite sure what you're asking but it appears that you are saying things that are hurtful to others. This happens when we don't "think" before we speak. Think things through before you say them and if something stills comes out that hurts someone, be quick to apologize and never forget what hurt this person so you know not to repeat it. It's good to "know your audience" but we can't always do this, in this case it's best to do more listening than speaking which allows you to learn a little about the other person. When you don't know someone very well, it's best to stick with general conversation that doesn't impact the other person. I hope this helps and take care!