How many times have you said something that you later regret?  Sometimes we get in a hurry when we are dealing with others.   We think that we must react quickly to please the other person.  Well, remember that you are only responsbile for yourself.  We CAN NOT control another person.  Quite often when we react abruptly it turns out wrong.  What if the rule was - you have to count to 10 before you can say anything?  When there is a deliberate pause in your speech, others may get uncomfortable and pressure you, but do it anyway.  You need to plan your action.  Be proactive vs reactive.  

What if someone upsets you?  Do you just say the first thing that is on your mind?  If you use the pause technique in this situation, you can catch your breath, use some quick restructuring to regain composure ("I got this" or "I am ok") and then decide what you are going to do.   Sometimes the best thing to do is nothing.   Think about the last time you put your foot in your mouth and consider what would have been different if you did nothing.  At minimum, plan your next move so you can gain a sense of control over your behavior.   This may not be easy because you may be in the habit of just reacting to everything that crosses your path.  Be kind to yourself, be persistent and keep trying.