Being optimistic isnt bad but having these expectations shouldnt really be having on someones mind and would really believing into something which should not really be like that.

Invest on what you can afford to lose and dont anticipate that it would make out some guarantee that you would make money in the future.Nothing is predictable or be known

and this is why you should prepare yourself on what would be the worst and same goes that when the market turns out to be good then you do know on what comes next.