CNBC's Jim Cramer said Tuesday that early January trading shows how quickly emotion can take over markets at the start of the year, warning investors not to confuse momentum with durability.Cramer said the market is being driven by three groups: momentum traders chasing last year's winners, "hope springs eternal" investors buying beaten-down stocks and companies that never should have lagged in the first place."We've seen these trends last as long as ten trading days into the new year, before we've got even ...