When we're told to touch our hearts, the majority of us touch the left side of our chest. This is the location where the organ is depicted in illustrations of Cupid, and it's often where good guys plunge their swords when finishing off the bad guys in the movies.
In truth, your heart is located ever-so-slightly left of the middle of your chest, behind your sternum. But why does it feel like it's located far left of center?
The left side of your heart is responsible for pushing blood to the farthest corners of your body. The right side delivers it to the lungs, which are directly next door. For this reason, the heart doesn't use much force to shuttle blood to the lungs, or else it would damage them. However, the heart gives a powerful push to send blood on its way through the arteries, and it's the left side of the heart doing this heavy pushing (or twisting, actually).
Although located in the middle, it's this powerful left-side pump that we feel, and the reason we Americans don't touch our sternums while saying the Pledge of Allegiance.