You can have a look at the DBT workbook by Matthew McKay and start some of the exercises yourself whilst waiting to start a group. Practice mindfulness to ground yourself in the present moment.
Similarly learning about Stoicism could help you too. There’s lots of simple explanations for beginners on YouTube. How to be a stoic is more accessible for modern readers over just diving into Meditations by Aurelius.
Unsupported browser
Work on building up your self esteem and core self identity . I can still have my moments, but growing older and becoming more comfortable in my own body was one of the main reasons I feel mellowed out and less reactive than I used to be.