Boldness
Boldness is not hesitating or being fearful in the face of actual or possible danger, courageous and daring.
I agree that if there is something that you have ever dreamed of doing and you know that you are bold enough to actually accomplish it then I think you should do it. Boldness definitely takes power.
Assertiveness
Assertiveness is being self-assured and confident.
I think it's true that assertiveness is a good quality to have because we all want to be confident in ourselves and have a high self-esteem but we don't want to be too conceited and put others down. We need just the right amount of confidence and I think that's what assertiveness is.