7 Mistakes Employees Make at Work That Keep Them Poor, Stressed, and Underpaid. Many people work for years without progressing, not because they are lazy, but because they keep making these career mistakes. 1. Stop believing hard work alone will get you promoted. You can be the hardest worker in the office and still be overlooked. Make your contributions visible, develop valuable skills, and communicate your achievements. 1. Never train your replacement without protecting your interests. Teaching colleagues is good, but don’t assume helping everyone guarantees job security. Build expertise that makes you valuable beyond one task. 1. Stop accepting every assignment just to impress your boss. Some employees cannot say no. They accept everyone’s responsibilities, become exhausted, and still get criticized when one task goes wrong. 1. Never gossip about your manager with coworkers. You may think everyone agrees with you until someone repeats your words to the very person you criticized. One careless conversation can damage years of trust.