In moments of extreme panic, dissociation or overwhelm, try "box breathing" for a grounding reset.
Tapping is another way to bring nervous system calm that works in a variety of situations of overwhelm, from dealing with tinnitus to having a panic attack.
A longer-term, preventive solution for emotional turmoil or overwhelm is to develop a meditation practice. Meditation is at least a 5,000 year old practice that originated in India and has come to be recognized the world over for its benefits to mental health.