Isiah didn't stop practicing for a long time , he was just not satisfied with the result, at first he saw the intensity of the dark rain as progression to his spell, and he thought that his hard work paid off, but after a long time, he just realized that he wasn't moving on toward what he wanted.
He thought that controlling his body and mind and powers were enough to make this spell work, but he released after hundreds of failed spells that he was indeed in control of his mind and body and of course his powers, yet those were not the only variables controlling the efficiency of that spell.
He forgot totally about exterior variables, the rain he summoned using that spell was from an unknown source, and being next to the sea was contradicting his own spell.
Isiah only realized this when he remembered what Eijar told him that day about the movement of the sea waves that he couldn't detect with his eyes because it was faster .
