When I need to slow down, but actual holding-still, breathing-on-purpose meditation or relaxation is too much for me, I draw. Here are some favorites:
1) The breath line. I close my eyes, put my pen on the page and draw upward on the inhale and downward on the exhale. I try to imagine that my breath is moving the pen. Sometimes I move my pen faster or slower, or draw shorter or longer curves – whatever feels like a natural expression of my breathing. Here are some from the other night.
2) Inhale / exhale spirals. I think that Lynda Barry got the world going on spirals: she says when you sit down to draw, start making spirals and don't stop - keep your hand moving - and do that for a few minutes, or until you're ready to draw, but whatever you do, don't stop to figure things out, just keep your hand moving. She says to make the spirals as close together as you can without them touching (if they touch, you're electrocuted and you start a new spiral).