When you talk too much you can do many things; lose your target audience completely where they shut you out not hearing a word you say, convince the person or persons you're talking to that you're not interested in their input whatsoever, or, even more damaging, convince your audience that you're really not sure of what you're talking about in the first place, hiding behind volume of information rather than quality. (get the picture re: rambling?)
Not only do others begin to avoid you like the plague, but in turn will not share their ideas and insights with you because they feel you're not interested.
If you even think you're rambling, then you are. If you find yourself struggling to keep quiet and listen, then stop the struggling and open up to the possibility that you don't know everything there is to know and the only way to counteract that is to practice effective listening.
Use the one minute concept. If you need more than one minute to get your point across, then you need to learn focus and prioritizing. If at that point the listeners want more information it gives them the opportunity to process what you've said and ask clarifying questions.
And if you know someone who does ramble, then don't automatically assume they're aware of it. Only through constructive feedback can they learn to recognise when they, are and make appropriate changes in their communication patterns.
You are doing them a favour in pointing it out in a respectful, constructive way.
Remember, people ramble for many reasons....if they're excited or nervous about doing a presentation in which case practicing those skills will combat the problem. They can be unprepared or not sure of the reason why they were asked to make the presentation trying to please everyone at the same time, therefore waffling back and forth.
It can be to cover embarrassment, being cautious, clarifying thoughts out loud or needing the interaction. For many it's because they live with "talkers" at home, can't get a word in edgewise so make up for it big time at work.
First step in improving is to be aware, to be mirrored and given constructive ideas for change with lots of practice in the (what I like to call) "short, sweet, to-the-point" methods of communicating.
It doesn't matter how knowledgable or intelligent you are. If you've lost your audience, no one will ever know.