In order to vigorously strive forward in cultivation and in Fa Rectification, a practitioner must strengthen his willpower. As Master said in the Jinan Lecture: "Sincerity is a prerequisite if you are to rectify your heart." (Chapter III, Cultivation of Xinxing, Falun Gong)
For a new practitioner, lack of a strong willpower may easily cause him to be hindered by postnatally acquired human notions, thus preventing him from going on with cultivation.
Lack of a strong willpower may also lead the practitioner to be dictated to by various attachments such as the pursuit of comfort, fear and laziness, and hence fail to step forward in clarifying the truth.
Furthermore, a practitioner needs to have a strong willpower when studying the Fa and doing the exercises, or he or she can be easily lost in busy daily life. Without a strong willpower, a practitioner could feel sleepy when studying the Fa or his mind might wander when doing the exercises or sending forth righteous thoughts; thus he might fail to achieve complete tranquility or accomplish the effect of righteous thoughts. As Master stated in the Changchun lecture: "You fall asleep while studying the Fa, you fall asleep while reading the book, and you also fall asleep while doing the exercises. You haven't even broken through the beginning stage yet. It's about willpower! (Lecture at the Assistants Fa Conference in Changchun 1998).
Without a strong willpower, we may also harbor our demon nature when overcoming tribulations, and we may unintentionally give people a negative impression of Dafa practitioners. Therefore, from now on, all practitioners should try to strengthen their willpower in cultivation, Fa rectification and truth-clarification. The above is my personal understanding. Please point out if there is anything improper.
Lastly, let us remember Master's article "Righteous Thoughts and Righteous Actions":
"A Great Enlightened Being does not fear hardship
Having forged an adamantine will
And with no attachment to living or dying
He walks his path of Fa-rectification openly and nobly"