While repeatable mechanics are key, I think pitchers need to be careful not to be too mechanical ... at some point you need to be athletic, turn it loose, trust your stuff and not worry about the results . Instead of breaking down every move you make, adjust your release point ... it you're up, work to get the ball out in front a little more - throw it into the dirt if you have to, but adjust !.
Regarding control, gain confidence thru prior success and know that you can repeat it . As a kid, I did this by throwing at targets ... all the time, with anything . Had a chalk target on the side of Mom's house and spent hours throwing tennis balls at the target ( warning - my Mom still likes to tell how many windows I took out ) . Took baseballs over to the school and threw at different parts of the backstop ... made games of it. Baseball is a game, and the skills I developed in these little games that I'd make up carry over...and help instill confidence in your ability to throw the ball where you want .
Be an athlete , not a robot !!