my aunt has had lupus for a long time and here are a few things she would share
love yourself. see you own self worth and don't ever doubt it.
take care of yorself.
don't feel guilty.
yes, many people cope just fine, don't take that to mean that you're weak or pathetic if you have a bad patch. like someone said, a flare up can last a long time. my aunt's lupus has been pretty severe and she suffers from many lupus related conditions. two years ago, she went into a coma after routine surgery. and even though she's feeling good nowadays, she has a bad days when she feels down and miserable.
we're not always there to support her and her teenage daughters are always sympathetic. so, while friends and family are a great support network, you also have to develop the support network that is always available too, that being yourself.
the other medical stuff, everyone has touched on so i have nothing to add. my thoughts are with you