On the final day of her party's conference, May rallied members, trying to address their concerns that the Conservatives are becoming increasingly directionless under the weight of Brexit by calling on them to look to a brighter future, Reuters reported.
The leader's fragile position has been put under further pressure over the last month after the EU rejected parts of her so-called Chequers plan and critics have stepped up calls for her to rethink her strategy for Brexit, the biggest trade and foreign policy shift for more than 40 years.
But with just six months before Britain is due to leave the bloc, she has so far weathered the Brexit storm, shrugging off a barnstorming speech by her former foreign minister Boris Johnson, which did little to hide his leadership ambitions.
On Wednesday, she was keen to show she was in charge of the Brexit talks.
"If we all go off in different directions in pursuit of our own vision of the perfect Brexit, we risk ending up with no Brexit at all," she said, a rebuff to Eurosceptic lawmakers who have published their alternatives plan for leaving the EU.
"And there's another reason why we need to come together. We are entering the toughest part of the negotiations ... What we are proposing is very challenging for the EU. But if we stick together and hold our nerve I know we can get a deal that delivers for Britain."
She also tried to return to the message she gave when she was appointed prime minister in 2016, promising to help those who feel "left behind", many of whom voted to leave the EU in the referendum of that year.
And in another call for unity, she attacked the main opposition Labour Party, saying their policies, including the renationalization of mail, rail and utilities, would mean increased taxes and drive away business.
Labour leader Jeremy Corbyn, she said, would "outsource our conscience to the Kremlin".
Her words were aimed at easing the growing frustration of some Conservatives who openly say their party is directionless, unable to set an agenda against the divisive rows over Brexit between competing wings of the party.
The pressure she was under from some in the party was underlined less than an hour before she was due to speak when Conservative lawmaker James Duddridge said he had submitted a letter calling on her to resign. Forty-eight lawmakers would need to write such letters to trigger a vote of confidence in the leader.
But Wednesday's speech seemed to have gone down well among the party faithful.
Foreign Minister Jeremy Hunt said on Twitter: "Congratulations Theresa May for a remarkable speech delivered with humor and passion. Firmness of purpose, clarity and conviction – EU friends do not underestimate!"