CFS patients will need to avoid stressful activities, and each patient's to=
leration for
stress will be different, and can change). It is nonetheless important for =
patients who
can exercise to do so, up to their level of toleration. But this should be =
done with great
care, since crossing the "invisible line" of exercise intolerance for this =
illness may prompt
a serious relapse, and may negatively affect the longer-term future course =
of the illness.