Dad frustrated because son wants to do it himself

Why doesn't my son want me to teach him things? From the moment he was born I've been looking forward to the time when I could teach him how to do all kinds of fun "guy" stuff. But now that he's old enough, he doesn't want me to teach him anything. When I try, he just says, "Dad, I can do it myself!" This isn't how I envisioned fatherhood. Any advice?