Knowing one's limit

Every person on this earth has 24 hours in his day. (God has been fair that way!) What differentiates a Bill Gates from a John Doe is the quantity and quality of work that Bill does in his 24 hours. This is what I have believed in for as long as I can remember. 

I would like to think of myself as an efficient smart worker. I have observed that I am usually able to get many more things done as compared to the next person. And, maybe, that's why I have done well in life till now. However, in the last few months, for the first time in my career, I am feeling that my plate is starting to get full. Earlier, I used to finish everything before my deadlines and I used to find time to do many extra things. But, lately, my schedule has become so tight that it's almost squeaking. I am barely able to get things done on time, and am usually playing catch-up instead of being on top of things. I am afraid that very soon I will start falling behind. 

My boss often says that every person has an upper limit, and that if a person can recognise and accept that, he will never have undue expectations from himself. Have I reached my upper limit? Does this mean that I have reached my full potential? Maybe I have reached my upper limit. But, I also believe that we, human beings, have this unique ability to improve ourselves and raise our upper limits. This is what separates us from the rest of the animal and plant world.  I cannot let this become my upper limit. So, I guess I have my task cut out. Instead of constantly handling the "urgent" things, I will have to take time out to reinvent myself and the way I do things. Am I being over-confident in refusing to recognise and accept my upper limit? Only time will tell. I don't know if I have undue expectations from myself. What I do know is that I cannot and will not stop trying to raise my upper limit. I owe it to God - as a Thank You for creating me as a human being, and not any other living thing.