Being sick is difficult, it is a reminder that you are human, that you- on a biological level- have flaws. Being able to work through sickness is a very admirable trait. It takes toughness and dedication to suffer through not only the sickness, but through your daily life as well. On top of everything you had to do, you have to deal with your sickness.
By sickness, I am mostly referring to the flu or the common cold, rather than much more serious illnesses. That brings another level of strength and admiration- those who power through serious illnesses. You have to be tough in those situations.
However, in terms of just being sick, you have to not forget to take care of yourself via medicine- this seems logical but I have encountered some people that simply forget to take medicine or not know what to do. In the midst of getting everything done, one might forget to take of themselves. Take breaks. Award yourself. Treat yourself.