set your heart/mind on something/on doing something
set (one's) heart on (something)
To resolutely determine to do or acquire something. When I was a little boy, I set my heart on becoming a fighter pilot. When Janie sets her heart on a new toy, she won't give us a moment's peace until we buy it for her.
set your heart on something
COMMON If you set your heart on something, you decide that you want it very much and aim to achieve or obtain it. Note: The heart is traditionally regarded as the centre of the emotions. She'd set her heart on an acting career. She admits that when she saw the flat Jeremy had set his heart on, her first reaction was horror.