Bitcoin is now my largest holding, courtesy of the monster 2020 rally that has continued into 2021.Bitcoin's meteoric rise illustrates the challenge of properly balancing risk management and maximizing return in your portfolio.Because 20 percent of your investments will contribute 80 percent (or more) of portfolio return and investments have price momentum, you generally maximize your returns by sitting and holding.Catalysts that could drive bitcoin even higher.New bitcoin buyers should dollar-cost average and add on pullbacks.