An emotional Sonia Gandhi, who retired as Congress chief - a position she had held since 1998, said "savage personal attacks" by his opponents had made her son and new party President Rahul Gandhi "brave and strong-hearted".
In her speech at the ceremony to hand over the charge of party President to her 47-year-old son, Sonia Gandhi said she was confident that "with a new and young leadership, our party will be reinvigorated and bring about the changes we need".
"India is a young country. You have chosen Rahul as your leader. He is my son, and it would not be suitable for me to praise him. But this much I will say -- while from his very childhood he has borne the experience of violence, the savage personal attacks he has confronted since entering politics has served to make him a brave and strong-hearted man.
"I am proud of his endurance and firmness, and I am confident he will lead the Party with a pure heart, patience and devotion," Sonia Gandhi said in her last speech as Congress President.
She recalled how nervous she was "that my hands were shaking" 20 years ago when she made her first address as Congress President.
"I could not think how I would manage to take charge of this historic organization. It was a formidable and onerous task that confronted me."
Gandhi reluctantly joined politics after her husband former Prime Minister Rajiv Gandhi was killed in a suicide bombing in 1991 -- seven years after her mother-in-law and then Prime Minister Indira Gandhi was shot dead by her own bodyguard in 1984.
She said until her entery into the political limelight, her connection with politics had been entirely personal.
"As you all know, it was through my marriage that I came into contact with politics. Indiraji was the daughter of a revolutionary family which had surrendered its wealth and ease for the Independence movement. Each and every member of this family had been to prison in the cause of freedom. Indiraji accepted me as a daughter and from her I learned about the culture of this country, about those principles on which this nation was founded."
She almost broke down and recalled Indira Gandhi's assassination in a choked voice.
"In 1984, when she was assassinated, I felt as if I had lost my own mother. That catastrophe changed forever the course of my life. I had a different view of politics at that time and I had wanted to keep my husband and children as far away from it as possible."
But circumstance forced her husband to bear "a heavy responsibility" despite my pleas, she said.
"Then, just seven years after the death of Indiraji, my husband too was assassinated. I lost my anchor and my support. It was many years later that I could emerge from my shell. Only when I came to feel that the Congress was facing a crisis, and that communal forces were gaining strength, did I feel compelled to respond to the call of the party workers.
"I felt that my turning away from this summons would negate the sacrifice of my mother-in-law's life and my husband's life. So I entered politics -- to fulfill a duty to my family, party and the country."
She said the Congress had only three state governments when she joined the party and was far from a government at the Centre.
"With all your continued efforts we regained our strength and one after the other formed governments in more than two dozen states."
She recalled how how lakhs of Congress workers had been with her in facing many challenges to keep the party united and focused.
"After 2004, together with some like-minded parties, for 10 years we gave the people a responsible and progressive government led by Manmohan Singh that worked for all sections of our society. We are proud that during this period we brought in rights-based laws securing for our poor brothers and sisters their rights to food, education, employment, information."
Sonia Gandhi said the challenge now was even greater with the Congress losing many elections.
"Since 2014, we have been playing the part of the opposition. Never before have we faced the challenge that we face today. The fundamentals of our Constitution are under attack. Our party has lost several state elections. But an exemplary energy fires our Congress workers. We are not ones to bend in fear, because our struggle is a fight for the very soul of this nation. We will never retreat from this fight."
She said the leaders and workers of the Congress, as the custodians of the ideals and principles of the nation, had a challenge to meet -- to safeguard "our fundamental principles" of India.
"This is no small matter. It is not power, wealth or self-importance that is our aim, it is this country - it is safeguarding our fundamental principles. We are all witness to the daily attacks against freedom of speech and expression, against our culture of diversity, and its replacement with an atmosphere of suspicion and fear.
"The Congress must look within in order to forge ahead. If we do not stand by our principles, we will not be able to wage this fight. It is a battle of righteousness, and we must fit ourselves in, in order to attain success."