Richard Harnack wrote:
All of the other methods mentioned are excellent for at home, however, in the middle of Shomenuchi Kokyunage or Munetsuki Kotegaeshi, quite possibly a little difficult to do.
Personally, I wouldn't lay down in the middle of a dojo and start meditating either unless I was the only one there.
The relaxation practice first mentioned by CrystalWizard when combined with an anchor phrase is very viable in the dojo. The process was designed for competitive athletes who tighten up when they shoot a free-throw for instance. You go to the line and by saying "relax now" it brings back a bit of that relaxation you have when not in the game or on the mat. A specific example that I could think of would be during a test and things get a bit harried. You pin your partner a second longer and say "relax now" to yourself as an adjunct to getting things a bit less harried. It's the same idea as taking a deep breath to relax only it's an organized conscious practice.