Before you try to stop your mind, or shut it up, there's a much simpler question to ask yourself first: what is the mind, actually? What is it made of?
If you don't know what it is, you'll keep fighting something you can't even see.
The mind is not the brain
Start by telling the two apart. The brain is the organ in your head. The mind is the set of thoughts you've gathered from your past experiences, the ones you use to analyse, think and draw conclusions.
If the brain is the hardware, the mind is the operating system installed on it. It got written bit by bit, out of everything that happened to you and everything you heard and believed.
A tool for living
The mind was meant to be a tool that helps you live. A tool serving the survival instinct: where's the food, where's the water, what's the danger to watch out for.
The trouble is, it grew far beyond that. It went past food and drink and got put to work for other agendas that have nothing to do with surviving or living.
Why we were so relaxed as kids
So when we say "mind", we're talking about a bundle of thoughts. Take the thoughts away and there's no mind left.
That's why as a kid you were relaxed, living each moment as it came, freely and innocently. The bundle hadn't got heavy yet.
As you grew up, the mind that bugs you now took shape. A bundle of thoughts piled up in your head that doesn't serve you, and the strange part is that you built it yourself, just without noticing.
Something that isn't there
And when we say "thoughts", we're talking about an illusion, something that doesn't exist. It's either a dead past or fantasies about the future, and neither of them exists in this moment we're in right now.
Try it now: the thought that's worrying you, is it about something happening this moment? Or about something that already happened, or hasn't happened yet?
The root of the problem
That's the root of it: you don't see thoughts as just thoughts, as something unreal. You see them as real, and that's what makes you tense and anxious.
So before you try to stop your mind, get to know it. When you see a thought for what it is, just a thought, its grip on you loosens bit by bit.
And if anxiety is weighing on you, getting in the way of your sleep or your work, talking to a professional helps a lot, and nothing stops you from walking both roads at once.