Being fatigued is different from just being tired. According to Dr Karin Olson, a University of Alberta professor (Faculty of Nursing), individuals who are tired still have a fair bit of energy, so although they may feel forgetful, and impatient, and experience gradual heaviness or weakness in muscles following work, this is often alleviated by rest. Fatigue, on the other hand, is characterized by difficulty concentrating, anxiety, a gradual decrease in stamina, difficulty sleeping, increased sensitivity to light and the limiting of social activities once viewed as important. Individuals with exhaustion report frank confusion that resemble delirium, emotional numbness, sudden loss of energy, difficulty both in staying awake and in sleeping and complete social withdrawal.
Unlike tiredness, long-term use of caffeine and other stimulants are generally avoided or minimised by people experiencing fatigue and exhaustion, as these substances "fool" the body into thinking it has more energy available than it really does.
So as helpful as your friends and family are trying to be with their comments, the fatigue/exhaustion suffered by chronically ill is actually not the same as tiredness. We, too, struggle with tiredness, when we are extremely busy etc but we struggle with fatigue too, which is by far more sinister than the tiredness.