Ineffective communicators mindlessly or thoughtlessly say and do things that they may later regret, they are ignoring which fundamental communication principle?

Effective communication implies a process where an understanding of a message between a sender and a receiver takes place.

Effective communication requires the sender to know the purpose of the message. This is what we know as principle of objective. The sender must know what he wants to transmit and what he's going to get with it, as a final result. That's the reason why mindlessly communicators regret what they say, because they didn't think it through. They didn't have a clear purpose or objective when they sent their message.      

i would suggest wrtiing it urslef

k12 has plaigsurism checkers