"If you deliberately plan on being less than you are capable of being then I warn you that you'll be unhappy for the rest of your life."
-- Abraham H. Maslow
You will be unhappy when you are satisfied where you are and don't seek better future. Then you will be asking why you are not promoted when you know you have the capability. But people never saw you perform better than where you are. How can you be promoted when they see you as someone who is suited to your work. How will they know you are capable as a supervisor or manager.