No no no no this bad terrible advice. I want my direct reports or colleagues to let me know when they are stressed or overwhelmed. Its important to let people know these things even if the cause is unrelated to work. Pretending you are not is just a recipe for disaster later on. A good boss or employer will work with you to find ways to help you through any troubles you are having. If you find yourself working in an environment where you feel you cannot communicate this, find another job fast and get out.