The idea that the mind controls the body sometimes comes across as woo or hokum. We are apt to become defensive, as if we are to blame for any problems with our bodies. Well, naturally, things do happen to make us unwell: viruses, accidents, whatever. And we all have our troubles. And not all of them are under our control.
But let's start with something simple. Let me ask you to lift up your right hand. You do it. Well, I asked to you do something and you did it. Seemed like a reasonable request and a reasonable response.
What if I asked you to lift your right hand and you decided not to? That's also a reasonable response. But if you notice what happened... there was the idea in your head to do it and you said "no, I'm not doing that, who the hell is she to order me about?" There may also have been a small twitch in your right hand, or your arm, or your neck, as your body prepared to do it. But you got in the way and said "no".
Or you could have lifted your left hand, if you were the kind of person who doesn't always know left from right. You could have wondered if you meant the right hand as I'm looking at you, which would be your left... and got caught in a loop.
So you see that your response to my request is entirely up to you. You can do whatever you want with it.
Let's try something bigger. Let's say you're at the office and you're the kind of person who wants to keep people happy. Say you're someone's personal assistant. They ask you to make coffee. You drop whatever you're doing and you run off and make it. After all, they need coffee. What you were doing can wait.
Or try this: you hear their request and you say, to them or to yourself, "I'll just finish this part of what I'm doing and then go and make your coffee. Maybe I'll have one myself." In a timely fashion you come to a stop, get up, go and make coffee, everyone's happy. If indeed coffee making is part of your job. If it's not, then that's another matter!
The point is that you are in control of your actions. You look after yourself first. Then you can look after other people better.