I believe in willpower as well as fate. I think that it is impossible to accomplish any great feat with out the help of others. Many people say "I did this and that" , but sometime I think that there is a bigger picture that they are not seeing.
First to have faith in oneself that has to be nurtured from young, so if you had good parents one should always thank them. Second, there is always influences in one's life as long as one interacts with others, so if you have good friends you should remember them and be grateful. Also know when to leave bad company.
Third there must have been those who have passed on knowledge and supported one's effort to make what ever great feat that is accomplished successful.
I have accomplished many great things in my life as well as made some stupid mistakes, but I am always looking at the big picture knowing that it is not my will alone. It is not all luck of all fate, it is a combination of many factors.
All I am saying is yes there is willpower, but remember the big picture.