Take some time every day to be focused on the environment around us. This can be the sounds, smells and sights as we walk, the water and items as we wash up, the sound of music. Whatever we choose, we need to loose ourselves in that experience, thus learning ourselves, and teaching the mind to focus away from negative thoughts. Notice what you can feel, what you can smell, what you can hear and what you are seeing.
If we find thoughts intruding, do not get stressed by them, just let them pass. Indeed, you can use Exercise 2 for this.
Whenever preconceptions, negative emotions or intrusive thoughts come to you, practise letting them pass. This is not suppressing them, which causes harm. It is instead being conscious of them, yet not giving in to them.
A useful visualisation is to imagine standing at a train station platform. As a train passes, imagine each carriage is a thought. The thoughts are real, and you acknowledge them, but in doing so you allow them to pass, just like the train
The above exercises become stronger with practice and over time become more and more powerful as your mind learns to operate differently in response to intrusive and negative thoughts, perceptions and emotions.
Practice these as often as you can in your daily life.
Learn from the above when NOT to listen to yourself