He said his plan to send 21,500 additional US troops to secure Baghdad and Anbar province "will need more time to take effect, adding "there will be good days and bad days ahead as the security plan unfolds".
Rob Reynolds, Al Jazeera's correspondent in Washington, said Bush's speech was "less a pep talk ... than a plea for patience from the American people".
In 2003, Bush announced that US troops were, "in the early stages of military operations to disarm Iraq, to free its people and to defend the world from grave danger".
Recalling the bombing that preceded the US-led invasion of Iraq, Saif Suham, a resident of Baghdad during the first days of the invasion, told Al Jazeera: "First thing there was the alarm, it started at about two or three in the morning ... I was with my family ... anything might happen we will live together or we die together. The sound - it was horrible, horrible."
Rear Admiral Mark Fox, a US commander during the 2003 invasion, told Al Jazeera that as the war began "there was a clear and distinct feeling" of being part of "a historic event".
But he said: "There's no doubt in my mind also that we did not understand the culture and we did not understand the complexities of that society as well as we should have."
Four years later a number of tactical and strategic shifts by the US government have proven ineffective in ending fighting in Iraq.
Washington's moral authority ebbed as the war continued and fell further when it was revealed that the CIA extradited several "high value" suspects in the US so-called "war on terror" to secret prisons in other countries for interrogation.
"The fact is [Bush] squandered our credibility, our legitimacy and even respect for our power, and that is a rather serious indictment," said Zbigniew Brzezinski, national security adviser under Jimmy Carter, a former US president.
Bush's handling of the war has damaged his own popularity and is said to have cost his Republican party its control over congress.
About 3,200 US troops have been killed in the war in Iraq which has gone on for longer, and cost more, than the White House ever predicted.
Meanwhile, Democrats are intending to promote a war spending bill in the House of Representatives this week that will effectively require the withdrawal of US troops from Iraq by the autumn of 2008.