LIBRA (Sept. 23-Oct. 22): Mystical poet St. John of the Cross (1542-'91) was one of Spain's greatest writers, but at a cost to him. When he was 35, a rival religious group imprisoned him for his mildly heretical ideas. He spent nine months in a 10-foot-by-6-foot cell, starved, beaten and tortured. It was there he composed his most renowned poem, "Spiritual Canticle." Are you inspired? Maybe you're in a tough situation now. It's not even one percent as tough as St. John's, though. If he could squeeze brilliance out of his lot, so can you.