I am a hard working ox but other coworker are not the same but they get promoted . Why?

Ronald, your coworkers may have other advantages that you may not know. They get promoted for a reason. Perhaps, you are a good employee in your leader's eyes. However, he might think that you can't be a good manager. Working hard is good but it's not the only criterion for beling a good leader. Also, it's possible that he may not know that you are working hard. Sometimes, you need make him to see how hard your word and what you have done.