“I expected the difficulties I’ve faced. It has been difficult. But I was aware it would be that way,” he told the BBC, as he prepared to start the second half of his four-year term on 7 August.
This milestone finds Santos’s popularity at an all-time low, down from some 83% last November to 47% now, according to the latest opinion polls.
This low rating is despite the fact that Colombia’s economic performance under his helm would be the envy of many a nation.
The past two years have seen Colombia continue the past decade of strong economic performances, with growth averaging around 5% and inflation kept low.
And according to official figures, some 1.2 million Colombians have moved out of poverty since 2010.
And with Santos in the presidency Colombia has become a business destination, attracting some US$13.2bn (£8.4bn) in direct foreign investment last year alone.
“More than two million new jobs created in the last two years, in the current international context, is quite an accomplishment,” said Santos,
“But maybe we haven’t been effective enough in explaining and showcasing our achievements,” he told the BBC.
Santos’s fall in popularity, however, seems to result mainly from his handling of the longstanding Colombian armed conflict, which many believe will make or break his legacy.
After taking office, he said he was willing to open peace talks with the leftist Revolutionary Armed Forces of Colombia (Farc) and other armed groups, provided certain conditions were met.
That was a marked change from the policies of his tremendously popular predecessor, Alvaro Uribe, who, as a result, broke with Santos and has been aggressively criticising him ever since.
Last year, under President Santos, Colombia also enacted a controversial law that aims to compensate an estimated four million victims of the armed conflict.
It allows damages to be paid to relatives of those killed, and seeks to restore stolen land to its rightful owners.
But the surge in Farc attacks registered under Santos’s government seems to have convinced most Colombians that the security situation is quickly deteriorating under his watch, while also making his dreams of a negotiated peace look naive.
The Colombian president, not surprisingly, sees things differently.
Santos acknowledges that there has been an increase in rebel attacks.
“However, it has a lot to do with us finally having a presence in places that had been under guerrilla control for the past 40, 45 years,” he told the BBC.
“That generates a series of reactions that, in turn, make people feel less safe. But if we look at specific indicators, such as murders per 100,000 inhabitants, we have the lowest figures of the last 30 years.”
Perception or reality, getting the security situation right will certainly be one of the main challenges of the second half of Santos’s presidency.
But he does not seem ready to abandon his more ambitious dream of achieving peace.
Santos says the rebels have not yet met his conditions for entering talks.
“Let’s say there have been steps in that direction, but they’re not sufficient yet,” he said.
But after two years in office, his outlook seems to be more optimistic than many of his fellow Colombians.
“I know what I want to do with this country, I have clear aims and I will achieve them,” President Santos told BBC Mundo.
Santos has so far refused to be drawn on whether he will seek another term come 2014.