The best stress strategy is the one you'll actually do when you're already overwhelmed. That rules out anything that requires an app, a subscription, or twenty spare minutes.
1. The ridiculously easy goal. Shrink the start until it's boring: open the doc, write one word. Starting is usually harder than continuing.
2. Long-exhale breathing. Inhale for 4, exhale for 6 to 8, eight times. A longer exhale settles your body faster than trying to think calm.
3. The brain dump. Everything on your mind onto paper, no order. Then circle only what you can act on today.
4. Change your location. Move one task to a different chair or room. Your brain links places with states, so a new place can break a stuck one.
5. Protect tonight's sleep. Pick a hard stop, lay out tomorrow's things, phone across the room. Sleep decides how much stress you can absorb tomorrow.
None of these fix a genuinely overloaded schedule. They make the next hour survivable, which is often all you need to get to the part where you can fix the schedule.