When I pitched, there seemed to be two reasons that it felt awkward to make a throw to a base: a) it's not off a mound - you get so used to throwing downhill that throwing off of a flat surface an instant later is very odd, and b) I wasn't using a pitching motion - similar to the previous reason, your body gets so used to throwing in a certain way that having to change it up at the drop of the hat can be tough. Now, I don't remember ever screwing up a throw as a pitcher (except for a pickoff once), but it still felt awkward much of the time. What I tried to do, provided I didn't have to make a hurried throw, was take a half-second to set my feet, switch my mind from "pitcher" to "baseball player" mode, and make a throw like I was just playing catch before the game. What's funny is that I was a very good infielder and outfielder, as well, and never had problems making throws from those positions.