With the exception of Jan, Bobby is the Brady with the most nagging insecurities and self-worth issues. His neuroses begin in the first season when he becomes convinced that step-mothers are unable to love their step-children (#10). From that point on, young Bob was a powder keg of self-doubt, and no season of the show saw Bobby's rise-and-fall detailed more prolifically than season two. But each time Bobby had to try try again, he persevered gracefully with all the determination of a seasoned chin-up champ.
Initially, Bobby is left with a crippling fear of heights after a treehouse climb gone awry (#36). But when it's up to him to save his precious pet bird, he climbs said treehouse without flinching.
Bobby is then looked over for the school's glee club in favor of Peter, Jan and Cindy (#41). As they carouse about, practicing "Loch Lomond" and reveling in their vocal abilities, Bobby's sense of worthlessness strikes again. To appease his fragile ego, Mike and Carol encourage Bobby to take up the drums. This leads the way for even more disaster until Bobby settles on the batton. And then household objects begin to break.
Perhaps no episode in the Brady canon explores Bobby's issues like #46, "The Winner." Marcia has all those trophies (apparently a sore point for both Jan and Bobby), Greg is unstoppable, and even Cindy has a trophy for playing jacks, a game of unparalleled skill. Bobby strikes out at everything, including magazine sales. So when Kartoon King makes a call for the best ice cream eater in the world, Bobby rises to the challenge. And fails. But not before the kids rally about to present him with a cheap trophy for Best Loser (and a huge bowl of ice cream as a consolation prize).
The latter years of the show would see Bobby succeed, especially against his siblings. The aforementioned chin-up skills set a precedent for excellence (#67), as did his talents as a safety monitor (#86), kisser (#99) and pool shark (#116).
The second season was a time of deep ponderance and exploration for Bobby. His maturation and confidence came only after giving his Brady all and accepting that failure was not an option. And that's real groovy.