Always be ready to grab a proper handhold, and remember, I have no clue what might happen in a train accident. Also remember that some trains are far more difficult than others. In any case, the idea is to stand freely without any hand support in the local subway train. I've found that actively shifting my center of mass can eliminate recoil, but I'm sure there are better ways than the way I am doing it. This discipline is simply that of occasionally checking on yourself.
Some people say they are best done daily.
Stretching Most people know some stretching exercises. They'll help keep you limber and relaxed in general. Try to catch yourself in the middle and gauge your centeredness, balance, and attitude. A mirror helps a lot. Ki should be always extending.