Giving your best at your work is not just about your skills and talents, or how experienced you are in your work. It is something else, namely how well your body and brain can coordinate and perform. If they are at their best surely you will be able to perform your best, but if they are not you will surely lose you capacity. There are some factors, however, that are accountable for your performing well or poor.
Sufficient amount of sleep is necessary to feel rested, and restore the lost energy for the day ahead. An undisturbed atmosphere for sleep is required in your bedroom, for which you should get rid of all sorts of stimulus like laptop, video games etc. and make it a calm place ideal for relaxation. A good amount of quality sleep can enrich your working capacity to a great level.
Breakfast is brain food, so taking a protein-enriched breakfast is beneficial for your body and brain, as this type of breakfast releases energy slowly and satisfy your hunger for long. You should refrain from craving for sugary snacks that give a momentary boost and suddenly drop your energy levels. Including some exercise in your daily routine can help you a lot. Exercise releases good chemicals that increase positivity and oxygen-enriched blood to help the brain functioning better. Even if you cannot make your time for daily workout you can surely park your car or get off public transport a couple of stop before so that you can walk the rest of the way to work. By keeping plenty of time in hand to get to work you can avoid the tension of being late, and thereby keeping yourself relaxed and unworried. This peace of mind can do magic to your performance.
Although smaller amount of caffeine can make you more alert and focused, too much can dehydrate you that can impair brain function. Drink plenty of water to stay hydrated. The body and mind perform their best if they are allowed to have some restorative breaks. If possible take regular breaks and get some outing and recreation to rejuvenate your energy anew.