Matthew 20:22
But Jesus replied to her, "You [really] do not know what you are asking for. Are you able to drink the cup [i.e., of suffering] that I am about to drink?" They [i.e., James, John and their mother. See Mark 10:35ff] answered, "[Yes] we are able to."
Mark 10:38
But Jesus said to them, "You [really] do not know what you are asking for. Are you able to drink the cup [i.e., of suffering] that I will drink? Or [are you able] to be immersed with the immersion that I am [to be] immersed with?" [i.e., to be overwhelmed with agony].
James 4:3
[When] you do ask, you do not receive it, because you ask from wrong motives, [just] so you can satisfy your own pleasures.