I see now that you are looking for ways to connect this quote to the Robert Frost poem, "The Road Not Taken." (In the future please try to put the text of your question in the upper box ("What is your question?") instead of in the lower section, which is used to associate topics with your question.)
Briefly, you might connect the quotation to the poem by looking at the concept of individuality as self-determination. This concept is certainly part of the quotation's intended meaning, though it is less clear that this is what the poem attempts to articulate.
One has to assume, however, that your teacher believes the poem is dealing with the notion of individuality and that this is the basis of a connection between the poem and the quotation.
If we take the concept of "choosing the road less traveled" and consider it in light of following one's own path or being true to one's individual self, then we can see the poem as advocating for a person's individualism (and thus speaking against conformity).
The speaker in the poem certainly chooses to "go his own way," as it were, but the meaning of this choice is not entirely clear. Is the speaker acting as an individual and choosing against the more conventional path through life? This may be true. Making such a connection is most likely the best way to link the poem to the quotation.
Yet, just for argument's sake, I would like to point out that the title of the poem is "The Road Not Taken" and so the poem seems to suggest that the central idea may not be individuality but may instead be simply that one's choices are inevitably permanent, irrevocable, etc. And a person can only choose once what path to take. All paths, except for the one a person follows, will be "not taken."
The quote, “Never be bullied into silence. Never allow yourself to be made a victim. Accept no one's definition of your life, but define yourself,” is attributed to Harvey Fierstein author of La Cage aux Folles and Torch Song Trilogy.
In considering quotations that relate to the ideas of bullying, victimization, self-definition and social activism, the first name that comes up for me is Martin Luther King, Jr. Although King received the Nobel Peace Prize and not the award for literary achievement, he was a great truly great writer capable of articulating difficult ideas succinctly.
Here are a couple of quotes from the work of Martin Luther King, Jr. that connect to ideas of speaking up and speaking out against injustice:
“Our lives begin to end the day we become silent about things that matter.”
“In the end, we will remember not the words of our enemies, but the silence of our friends.”
“There comes a time when one must take a position that is neither safe, nor politic, nor popular, but he must take it because conscience tells him it is right.”
Looking at literature for more writers interested in self-definition and issues of personal advocacy, we might do well to turn to the Transcendentalists of 19th century America. Ralph Waldo Emerson, Henry David Thoreau and Walt Whitman were all writing during the same period and each was interested in expressing a truth of self that had social, political and spiritual implications.
This quote is attributed to Emerson and it nicely summarizes a point of view placing self-definition above its converse (allowing others to define you):
“To be yourself in a world that is constantly trying to make you something else is the greatest accomplishment.”
Many American writers took up a similar approach to literature (and to life). Authors like novelist Henry Miller, poet/novelist Jack Kerouac and poet Allen Ginsberg are often cited as individualists with a spiritual bent as well as writers whose vision bordered on the political.