We understand illness as a finite process: you get sick, you are treated, you get better or you die. Chronic illness is the wrench in this process. Chronic illnesses change what people are able to do and, thus, who they are. It can be very difficult, especially with our cultural focus on strength and working through obstacles, to accept that chronic illness exists or isn't a product of laziness. Especially when it's an invisible illness and there are no obvious outward signs. Most folks with a chronic illness are likely to downplay the seriousness of it because few people want to know or can handle the emotional difficulty.
Friends and family often are forgotten or overlooked when talking about chronic illness. That is a shame. The entire family deals with the illness; a family shares each others' joys as well as struggles. Family members may feel guilt that a loved one is suffering and they are unable to help. The love and support of family is the best help anyone can receive! The whole family will grieve the loss of one member's health and the change to the family. The ill person will have to grieve who she was and learn who she can become. This process is difficult and each member progresses at their own rate but supporting each other will help tremendously.
Friendships are difficult in their own ways. All chronically ill people have lost friends, especially if they're hospitalized or homebound. The friends who do stay often find it difficult to understand the illness or how their friend has changed. Friends often are nervous or unsure to ask questions about the illness. Most often chronically ill people are happy to talk about their situation, especially with friends. Simply saying, "Do you mind telling me more about your illness?" is a great way to start the conversation. Asking a disabled person, "What do you do all day" is something you may wonder but not the best conversation starter.
If your primary connection to a friend was through physical activities you don't necessarily need to give that up. A milder version of the activity may work, or something different that retains an essence of the original. Even sitting on a park bench is a big deal for someone used to staring at their own four walls! You'll have more time to talk and learn about each other. Illness can teach a great deal and you may find that your friend has a greater capacity for caring and empathy.
To those playing a supporting role: please don't forget to take care of yourselves! The support system won't work without you.