Five ways to manage flashbacks - CRASAC - Coventry Rape and Sexual Abuse Centre

Tell yourself that you are having a flashback. Remind yourself that the actual event is over and that you survived.
Focus on the present. Look for differences between then and now.
Do what makes you feel safe. This might be curling up in bed, wrapping yourself in a blanket or, if in public, finding somewhere private.
Breathe. Take slow, deep breaths by placing your hand on your stomach and taking deep breaths. You should see your hand move out with the inhalations, and watch it fall in with the exhalations. When we panic, our body begins to take short, shallow breaths, and the decrease in oxygen can make you feel more panicked. Deep breathing is important because it increases the oxygen in your system and helps you move out of anxious state faster.
Ground yourself by using the five senses:
- What do you see? Make a list of the items in the room; count the colours/pieces of furniture
- What do you smell? Breathe in a comforting scent or focus on the smells around you. 
- What do you hear?  Listen to the noises around you or turn on music. 
- What do you taste?  Eat or drink something you enjoy. Bite into something sour such as a lemon – the bitterness can help to bring your senses back to the present.
- What does it feel like? Hold something cold, like a piece of ice, or hot, like a mug of tea. Put an elastic band or hair tie around your wrist and ping it as firm as you need to help to bring you back to the present.