Stress. Everyone knows what it feels like. Tight shoulders. Headache. Insomnia. Upset stomach. Everyone knows what can trigger it. Rush hour traffic. Deadlines. An insensitive boss. A toddler having a day of tantrums, unexpected bills, or taxes. We also know that too much stress can actually make us ill. Ulcers and high blood pressure are prime examples. A recent study noted that 19 percent of employees who call in sick on any particular day do so because they simply felt they needed a day off.