When you enter your place of work you become a different person, you play a different role. Suddenly you have to be more professional, assertive, alert, polite...basically you have to be Superman/Wonder Woman. You need to solve problems, come up with cost-cutting solutions (it's all about cost cutting these days) and then do the usual basic admin as well. Time constraints and deadlines are always lurking behind the scenes. You are a different person at work compared to anywhere else.
At work your guard is up, you are under pressure, you haggle with clients and even your own colleagues, you race against deadlines. You are more stressed and highly strung in the workplace.
Today I will not argue about the merits and disadvantages of having to change persona's. What I want to get across is that you cannot let your work persona engulf your other persona's and come to engulf you. You are a brother, sister, mother, father or friend to at least one person.
The danger comes in when you can't stop thinking about work when you walk out of the office every day. You bring your assertiveness, impatience and stress into the home. You find yourself being abrupt with the smallest transgressions your parents/partner/kids commit. When you forget to switch modes it can turn you into an intolerant, ugly person. You become a walking bundle of nerves and your mind is always at the office: whether you are at home or holidaying in Hawaii.
When you clock out at work, make sure your mind clocks out too. Refuse, absolutely refuse, to think about work. Don't talk much about it at home either. You can deal whatever pending issues you may have tomorrow or next week. Your loved ones need you, not Wonder Woman, not Superman.