Having a little problem with my key bindings, could anyone help?

So I've been practicing smart casting and I can't stand using the shift key, so I figured I would edit the configuration file and switch it to something I feel more comfortable with, the space key. Now when I play, regardless of whether I hold down the space key or not I always smart cast. It has something to do with the space key because I changed the bindings to something else and it didn't smart cast. Could anyone help me with my space bar problem, I really wanna be able to smart cast with the space key instead of the shift key.