Why did you know the etherium will be you sure ?

Ill think no one can be sure on when etherium will take to a high price again, But as of now it was good for us also that would be etherium are still in $200 than back to $100. Will all suffer to hold our etherium to sell it to a high price, And Ill think for now this will be a chance to sell it or buy more etherium because someone said in this forum etherium be get to $300.