“One of the first things you learn as a manager is that your own performance doesn’t matter anymore. You might have gotten promoted by being a hot shot, but once you are in a position of responsibility you have to get others to perform in order to succeed.”
All the things you were good at now have little or no value, you need a completely different set of skills. Additionally if you are really good at your current job and wondering why that promotion is not coming to you, it is the same answer. Managers and Employees are different skill sets.