It sounds like you're on the right track already, with your desire to work hard and make your boss like you. I would still take lunch breaks, though, so as to keep your strength up with food.
You don't need a spell to open yourself to positive energy; I would just take ten minutes before work to sit in a comfortable position, close your eyes, and meditate. Concentrate on your breathing at first; if other thoughts enter your head, just gently bring your attention back to your breath. When you begin to feel relaxed, consciously start to draw to you the needed energy: take up the energy and desire to do well and work hard through every breath. As you inhale each time, mentally hold and imprint this intent and desire for success. You will feel it spread throughout your being...
...then open your eyes, stretch, and go be a model employee.