Sometimes having a focal stone can help one to get centered. However if some nasty bug is making you ill than the stone will help keep you on a nice straight path even when feeling at your worst. There are so many stones that help and heal most everything. Blue Lace Agate is one the the most powerful of healers, prehnite is a superb area cleaner and so many more.

Read a bit and you may find one or two for you
http://www.chrystalpaths.com/whatstonesdolist.htm