Marijuana stocks were on a tear leading up to the opening of Canada's recreational marijuana market last week. However, pot stocks are tumbling since then and that could have you wondering what's next for this emerging industry. There's little doubt the marijuana market is undergoing significant disruption, but that doesn't necessarily make every marijuana stock worth owning in portfolios.  A little perspective It's tempting to react to short-term moves in stocks, but it's usually best to be proactive. Instead of buying and selling on the market's whims and whispers, savvy investors ride out tough times like this by sticking to discipline and remaining objective.