You should include the same advice that is given for exercise, it can and should occasionally be a bit painful but you have to discover your safe limits and only push yourself a little past them each time. You don't want to rack weights in 45lbs increments until you tear a muscle, you do it in 2.5lbs or 5lbs increments and practice for several sessions of work/rest at the same level for a while before making another small increment. People often quit both exercise and meditation because they just try to push through the pain and often end up with negative results due to injury or emotional and cognitive strain in the case of meditation.