I once worked with someone who had body language that you could read like a book. Stern looks, sad demeanor, very angry looking at times, interrupting while you were talking, especially when they were not in agreement, by harrumphing, sighing and rolling the eyes. It was disconcerting, but this person didn't appear to be aware they were doing it.
I think the first step is to acknowledge you are doing it and recognize that it as a problem. Once you realize that it is happening, you can watch for it and correct your behaviour. You have to look at yourself as a total package with hard skills (such as what you need to do to get the job done) and soft skills (such as how you are perceived by others, how you treat people, how you behave around people). You can be the best there is as an organizer, event planner or trainer, but if you don't come across as friendly or approachable, you will not be successful.
I was at a course recently for new supervisors and they recommended smiling on the phone. It is hard to smile without it changing your outlook and reaching others, even over the phone. Just the whole thought of smiling for the sake of smiling, would put a smile on my face. I am smiling just picturing it.
Another thing that has helped me is by seeing myself in a video, or in a photo. Especially when I am not aware of it. Sometimes I have had the sternest look on my face that would even scare me. No wonder people are intimidated. I think when we are very focussed on our work any interruption can be seen as intrusive.
Depending on where you work, it may matter even more how you present yourself. For example, if you are the first person people meet, then you have to train yourself to stop, smile and focus on the person you are greeting. Never have half an eye on them and the other reading a document, typing an email or tidying your desk. Turn around to greet them if your back is to them. Yes, it is an interruption, but showing bad body language will not help. If it is a constant interruption problem, then you need to deal with that issue and approach the person separately. Communication is better said out loud. People read different signals so don't leave it to chance.
Sometimes the position of your desk and computer can solve the problem. If it is an easy thing to do, have your desk moved, or move your computer, so your back is not to people when they come into your office space. It may be hard at first, especially if you are busy, but take the time to face the person and show them respect as a human being by acknowledging them and if you are busy just say, "I'm sorry, but I am extremely busy right now, can I get back to you later?" Or suggest they send you an email and when you have a moment you will get back to them.
My boss is a very focussed person and he doesn't like it if I interrupt him, although many times I am waiting for an answer and can't move forward on a project unless I hear from him, but I have learnt when I see him focussed to back out of his office and either write it down to ask when he comes up for air or schedule a time with him when we can talk face to face. You should ask yourself before interrupting, "Is it really that important that I get an answer right this minute or is it just me wanting the answer right now?" You will be surprised how many things can really wait. Since you are the scheduler for your boss's calendar then setting yourself weekly meetings will be a real help to cut down on the interruptions. Of course, my boss interrupts me constantly throughout the day, but then again he is my boss and I am there to assist him. I have also been an assistant for many years and have learnt that interruptions are just a matter of course in this profession. They are going to happen so you need to learn to expect them and plan for them in your day.
If you have an office door, close it when you are in extreme focus mode. Or try a bit of humour if you are in an office cubicle and put a sign up such as, "Deadline to meet, enter at your own risk" and have a funny cartoon picture of some frazzled person with stacks of paper. You are getting the message across, but doing it in a humorous way. Don't overuse it though or it will lose its effectiveness and if you greet the public, this would not be a good first impression to give.
I will not say I have mastered being the calm, professional and poised work colleague all the time, but I've certainly come a long way by recognizing that there is always room to improve. After all, we are all a work in progress.