You manage stress by disabling the automated thought process of cognitive appraisal that triggers the stress response. This is done by developing your ability to pay attention to the reality of the moment.
This stops you paying attention to the thoughts that you routinely use to evaluate what is happening.
Developing mindfulness enables you come to your senses and break the habit of automatically triggering stress. For example, Mindfulness-Based Stress Reduction (MBSR) therapy was developed to facilitate stress relief.
But you can train yourself every day to pay attention to the moment rather than paying attention to your thoughts. These short mental exercises should be done each morning.
A couple of points to note. The thoughts you use to evaluate threat and trigger stress are thoughts you learned in your childhood. Very often these thoughts are self-defeating or self-sabotaging.
Research shows that we routinely automatically select negative over positive thoughts when processing the reality of the moment.
Stress is something you do to yourself albeit automatically. This means that you can choose to stop doing it to yourself.