Resources
I'll be adding more to this section so check back soon. Different things work for different people, if we're working together we can discuss how to adapt these resources to your specific needs and which may work better for you.
Meditations
54321
I really recommend the 54321 meditation as it's a simple, focused, grounding mediation. You don't need to clear your mind and you can do it anywhere: home, work, tea break, while doing the washing up etc. It only takes a minute to do so doesn't take out time if you're stressed and can help you pause and refocus.
If there's part of you that's hyper vigilant, ask that part to check around you for imminent danger. If there's nothing you need to act on immediately to keep yourself safe, ask that part to notice that and then focus on noticing the below the things. You are noticing that you are here in the present not back somewhere in the past in this exercise.
Notice 5 things you can see. Try and notice small details like light/shadow, textures etc
Notice 4 things you can physically feel. The ground beneath your feet, any other points of contact with your body (chair, bed etc), clothing, any jewellery or glasses you're wearing, perhaps your hair on your neck, whatever is relevant for you in that moment.
Notice 3 things you can hear. Sounds outside or inside, bird song, street noise, whirl of a computer, your breathing etc.
Notice 2 things you can smell. Is the air fresh or stale, warm or cool? Lift your hand to your nose if you need to for an additional smell or to notice your breath against it if you don't have a sense of smell.
Notice one thing you can taste. The taste in your mouth maybe toothpaste, coffee, the last thing you ate.
Take a few deep breaths.
Dreams and Nightmares
For people who have nightmares or troubling dreams I recommend trying the dream completion technique by Justin Havers: