Fritz Perls, the famous Gestalt Therapist who is most famous for that lineage of therapeutic tools, used to say that anxiety is the gap between now and the future. What he meant is that is that anxiety is a “now” experience – it is accompanied by a lack of breathing very deeply. Many people can end an anxiety or panic attack by merely focusing on their breathing, noticing that they really are not breathing well at all – and the vast majority of the time, it is because they are telling themselves thoughts that are creating fears about the future. These can include telling yourself you have failed about something in the past, but the anxiety is caused because you are afraid that something will happen to you in the future.
The only way to calm down from an anxiety or panic attack (without medication) is to focus on the present moment experience you are having, breathe gently and slowly, really become mindful of the present moment and give yourself compassionate and gentle thoughts about whatever it is you are concerned about. Bringing a gentle, compassionate mindful awareness to this present moment will almost always lessen the pains of the anxiety or panic and allow you to relax your body and mind.
Usually anxiety is about fear of some catastrophic outcome in your life, very often, the anxiety (believe it or not) is keeping you from experiencing emotions that you perceive as threatening in some way. With practice and help, if needed, you can learn to “breathe into” your experience and bring a mindfulness to it in your examination of what you are really experiencing – and learn to “grow muscles” for experiencing your emotions in a way that they can be handled.