Keep the sense of relaxation in your feet and hands as steady as possible by comparing one side to the other
"No matter how the breath is cycling through the rest of the body, keep the sense of relaxation in your feet and your hands as steady as possible. It doesn’t have to be an enormous relaxation, just enough for you to know that it’s more relaxed than before. One way of checking it is to compare one hand to the other, one foot to the other. See which one is more tense and then allow it to relax as much as the other one." ~ Thanissaro Bhikkhu "Grass at the Gate" (Meditations3)