I try to ask myself a lot of questions when I need to ground myself.
How am I feeling right now?
Why do I feel this way?
Can I work out the root cause of this feeling?
What do I need to feel better?
Is there anything I can do for myself right now to make this better?
How will I avoid this next time?
It helps a lot, especially if I write it down in the exact moment I'm feeling something :>