They don't give up no matter how hard it gets, they dig deep and fight through each day.
They are empathic to the pain of others.
Knowing what it's like to live in constant pain, those with a chronic illness tend to have more empathy and understanding for others in similar situations. They're often the first to lend a helping hand when needed.
They often suffer in silence.
Acutely aware that others may not want to hear about their pain, many people with chronic illnesses will suffer their hardships quietly. They may miss social engagements because they are too ill to attend, but will downplay their non-attendance.
They become very good at pretending to be well and often don't look ill. This may be because they have made an extra effort with their appearance to mask how they really feel, or they are managing their symptoms with medication so they can get through the day.