"I think in Iraq there will always be political conflicts, there will always be, as in any society, sides drawn between different factions, but I really believe Iraq as a whole is on the right track."
Clinton said there were going to be bad days, but "I don't know of any difficult international situation anywhere in the world or history where there haven't been bad days".
She arrived a day after suicide bombings killed 60 people outside the most important Shia shrine in Baghdad.
At least 88 people were killed on Thursday by suicide bombers in Baghdad and Muqdadiyah, north of the capital, in what is seen as Iraq's deadliest violence in more than a year.
Violence, which was high following the 2003 US-led invasion, has dropped off recently, but the latest bombings come amid an increase in high-profile sectarian attacks that have raised concerns about the abilities of Iraq's security forces.
The Pentagon will hand over responsibility for most urban security in about three months as part of the US government's goal of a complete exit of forces by the end of 2011.