You are not your thoughts. Your brain does what it does, it processes information, it does this without you, when you dream, when your thoughts wander, your brain is doing what it does just as your lungs do or your heart.
Be the watcher of your thoughts just as you can be the watcher of your breathing. You can put your attention to anything your body- which includes your mind. Your body is experiencing and your mind is interpreting, with or without your attention. What we experience can be mindless or mindful.
When we let go of attachment to our thoughts we are still using our mind but it is not our mind that is running things it is our higher (deeper, truer...)self.
Don't try to switch off your thoughts, just notice them, especially when you are beating yourself up.
We say things to ourselves that can be horrible. When it is too hard to listen or shut up the monkey in the machine notice with your other senses and turn your attention to what you can hear, how your legs feel, what you are sensing, smelling, seeing or touching. Let go of believing what you are thinking. Practice being.
Try answering this answer this question.
What is your next thought?
Try this 13 minute guided meditation with Ally Hamilton