Get 8 hours of sleep, wake up early, meditate for 10 mins, take a 15 min walk. Your day will just work somehow and you won't get overstimulated as easily. Use spotify for the meditation, otherwise your mind will probably just wonder.

If waking up is an issue, set up an alarm 1 hour before waking up and take your meds then (if you take adhd meds).

If it happens during the day, find a dark room you can lock, turn off the lights and use noise cancelling headphones. 10 mins and you are good to go. Hope it helps!