Confidence and aggressiveness is something within you that you have to find and once found, figure out ways to bring it out in your daily life. I believe it has a lot to do with upbringing, childhood activities and the type of environment you have been in and are currently in and around.
I personally have always been the outdoors and active type; pushing the limits on much of what I do, whether it was sports as a child, growing up in a rough neighborhood or my career. Much of the confidence I have I attribute to my upbringing, my childhood and high school years. It's carried with me through my time in the Marine Corps, as a former cop and even now in my new career.
My advice would be to find something that you may have once thought of doing, but haven't because you may have been unsure of yourself and go for it. For instance, I started taking Tang Soo Do (Korean Martial Art Form) when I was 8 years old and was nervous as hell, but enjoyed the hell out of it and learned so much. It also built a foundation for my wrestling career in school and so on and so forth.
I'll leave you with a couple of quotes from some very confident and assertive individuals:
"We gain strength, and courage, and confidence by each experience in which we really stop to look fear in the face... we must do that which we think we cannot." Eleanor Roosevelt
"Confidence... thrives on honesty, on honor, on the sacredness of obligations, on faithful protection and on unselfish performance. Without them it cannot live." Franklin D. Roosevelt
Best of luck to you Bro! I'm sure you find a way to find the confidence you desire and bring it out of you!!
Regards,
