To do your best simply means that if you start a task, complete it completely. See it to the end. Whether it be as simple as making sure the trash you throw away actually goes in the trash can or completing that big Dreaded Project, complete the task completely.
Completing a task completely accomplishes 4 important things.
1. It ensures the job is done and done well.
Whether you are an employee or a student, if the job is not done well there are consequences. You will most likely have to do it over again or earn a poor grade. If the poor performance continues, you will be out of a job or out of school. Plain and simple. Employers and teachers are not going to coddle you forever, so do whatever it takes to complete the job.
2. It gives you a strong sense of accomplishment and confidence.
When you do your best and complete a task completely, there is an instant sense of confidence and peace that can come no other way. If you start cutting corners and taking shortcuts in your work, it will negatively affect your psyche and that negative feeling and energy will spill over to the other areas of your life. However, when you take the time to complete the task correctly and completely, you can feel great knowing that you have done your best and have seen the task to the end. By completing the task completely, your psyche will yell, "Yay!" and you will feel pretty stupendous about yourself. It's a great feeling.
3. It gives you energy to complete the next task.
Now that you rocked the initial task, a source of energy comes out of nowhere and, "Boom!" You are ready to tackle the next thing. Bring it!
I remember having to read multiple textbook chapters for an MBA class. I am not the fastest reader, and with a full-time job and a full-time family needing my attention, staying up late into the night reading case studies seemed a bit overwhelming. However, by taking the time to actually read the first chapter, I amazingly had a new sense of determination to get after the next chapter, and then the next. I could either spend my time crying and whining about it, or I could conquer it one paragraph at a time.
4. It is simply the right thing to do.
It has always been God's will for us to do our best and give our best for Him. I am reminded of the verse: "Whatever you do, work at it with all your heart, as working for the Lord, not for men" (Col. 3:23). Even if no one else will see what you have done, God will. God will reward you for doing the right thing, and completing a task completely is always the right thing to do.
So no matter how bad a day you have had or how unproductive you have been up to this point, START NOW!! Follow through on what you need to do and you will have more time and more energy to do the things you want to do.