Washington, Sep 4: In a letter left on Inauguration Day for US President Donald Trump that was both congratulatory and cautionary, former President Barack Obama urged the incoming President to guard democratic institutions and traditions, and "sustain the international order." "This is a unique office, without a clear blueprint for success, so I don't know that any advice from me will be particularly helpful," Obama wrote in the letter, which CNN published on Sunday. "Still, let me offer a few reflections from the past 8 years," The New York Times reported, citing the letter. The letter highlighted the concerns of a departing president who acknowledged the enormous responsibility of the job domestically and on the world stage. Obama wrote to Trump, a billionaire who had family wealth and made fortunes in real estate, that "we've both been blessed, in different ways, with great good fortune," adding, "Not everyone is so lucky." "It is important to "build more ladders of success for every child and family that's willing to work hard," he wrote. He emphasized that "our wealth and safety" depend on maintaining "the international order that's expanded steadily since the end of the Cold War." He also made a case for preserving "instruments of democracy" regardless of what the "push and pull of daily politics" may bring. Trump has shown the letter to White House visitors, and one of them shared a copy with CNN, the network reported. The White House did not immediately respond to a request for comment on Sunday. It is a tradition for presidents who are leaving office to write letters to their successors offering advice and well wishes. When George W. Bush left the Oval Office, he wrote to Obama: "There will be trying moments. The critics will rage. Your ‘friends' will disappoint you. But, you will have an Almighty God to comfort you, a family who loves you, and a country that is pulling for you, including me." Obama advised Trump to spend time with friends and family, and wrote: "Michelle and I wish you and Melania the very best as you embark on this great adventure, and know that we stand ready to help in any ways which we can." He wished Trump "Good luck and Godspeed," and signed it "BO". Trump has spent much of his presidency trying to undo the Obama administration's policies and regulations, leading The Washington Post to keep a tally of the uprooting. Even so, Trump has spoken warmly of the letter, telling ABC News in January that it was "beautiful" and "complex." "In fact, I called him and thanked him for the thought that was put into this letter," Trump said.