Working without taking a break will not make you more effective. This is because you will get tired and lose your train of thought. But when you take a break, you are able to recharge and come up with better ideas on what you need to do. The sooner you realize how much your body can take, the better it will be for you.
Unfortunately, some people waited until they fell sick before they took a break from their work. They pushed themselves so hard that their body could not take it anymore. You see the body will demand rest if you refuse to take it willingly. That is why there is a saying that all work and no play makes you a dull person. Do not wait for sickness to force you to slow down.
Plan your life so that there is time to work and a time to rest. Even the bible says there is a time for every matter under heaven. You cannot keep going indefinitely. Wisdom is in finding out what time it is and to adhere to it.