I consider a healthy person to be someone with an overall state of happiness, well-being, and someone who is able to carry out every day tasks along with being free of illness or disease. The criteria I used to define health comes from my personal experience along with media portrayal and how individuals carry themselves when under distress and unhealthy state versus their normal healthy state.
On the other hand, I see illness as when one does not feel them-self as result of sickness of some sort. As result of illness, people tend to be un-social, fatigued, or incapable of handling simple tasks whether it be from soreness of body or a lack of concentration or recollection. I consider my criteria of illness to come mostly from my personal experience and family interaction. Growing up especially as young children, my sister and I were taken extra care of when ill. However, if we were so ill that we were not able to make it to school then it could be assumed we were too ill to participate in normal activity outside of school. With that in mind I was not likely to act ill unless I was truly fatigued and felt sick to my stomach. In regards to this, I was taught not to take illness for granted.
I think it is hard to say whether anxiety is truly an illness or not. Anxiety is a change is mood dealing with apprehension and fear. I agree that anxiety deals with high levels of distress but do not find it be an illness at acute levels. However, since chronic levels of anxiety lead to visceral organ failure dysfunction in which case an individual is likely to develop diarrhea, tachycardia, sweating, tremors and dizziness. At this level I would consider anxiety an illness.
I believe insomnia is another condition that could be considered an illness in some circumstances and not in others. Given that it may just be that the individual loses an hour or two of sleep, I do not find it to be an illness. However if insomnia reaches the point where an individuals mindset is altered in that they cannot function on a daily basis or can be considered psychotic then I believe insomnia to be considered an illness.