No matter how much work is ahead if you are passionate and determined to complete a task then it shouldn't matter. If you quit a sport, move to a different country and there seems like no possible way to ever play again your passion for the sport should push you to go to the gym and continue training. If you take harder classes at school you should complete work before the due date if you really love the subject. No matter what it takes.
People will often make a lot of excuses (including myself) of why they can't do something. There are a few types of people in this world. Some of the most common are people who do, and people who just let life go by. One type of person that is also very common is people who say they do something, but they don't actually do anything. Every type of person will make excuses every now and then, some more then others. What makes a successful person successful is their ability to overcome slipping into bad habits and maintaining a steady work pace.
In the end nothing is really difficult if you are up for the challenge. When your arms and legs give out, or you are too tired to study any more. Devotion and dedication should kick in and give you that last bit of energy to finish. It may be hard to find at times but I do believe that everyone has the capability to be great at something. Which in some cases is not a good thing because that something might be terrible.. like kbut in most cases it is a good thing.