You battle with that little voice that keeps telling you to do what you know you shouldn't do. Your heart wants your fitness, your health, your super sexy body, but that little sabotaging voice wants those cakes, cookies, pizza..
The shoulder makes the arm I always say, so in order to get that nice round shape, you have to hit all three head of the shoulder. Shoot for 15 reps and pick a weight where you begin to struggle around 12 reps. If you need to rest a moment to finish them, that's ok.