Grief is much like an actual, physical illness, especially in the beginning. Your appetite diminishes, you can't sleep, you sigh and wring your hands, cry, shake, feel panicky and nauseous, breathless, have tightness in your throat and chest that makes you think you are having a heart attack. You can't think straight and forget things-you have trouble putting your thoughts into words. You become fearful, angry, hostile even, or apathetic. You sense the presence of your deceased sibling and think you are going crazy. Your grades slip and you don't care. You withdraw from people. And worst of all, you think it will always be like this-there is no end in sight.
These are normal grief reactions. The symptoms look a lot like a major depression. One difference, described in psychological literature, is that with grief, you don't feel the same loss of self-esteem that you do with depression. In time, with support, you get through it.
There are other pictures of grief, however. If your sibling was ill for a long period of time, you have probably been grieving bit by bit, all along. The death itself may be met with relief as the primary feeling. Grief differs with each individual, since individuals all differ from each other.
Dealing with grief is made easier by an attitude of discovery and acceptance of your own feelings. People who tell themselves "I shouldn't feel this way," are berating themselves needlessly. The struggle to control feelings and keep them from surfacing is far more painful than feeling and expressing them.