President Michael D Higgins used his new year message to the diplomatic corps in Ireland to warn of the need for "continuing vigilance and commitment" in deepening the peace process.
In the wake of the loyalist violence during the union flag protests in Belfast, Mr Higgins said the street disturbances were a "sharp reminder" to all sides.
"Any complacency about the need to nurture that fledgling peace, to build confidence on the ground and to advance reconciliation between communities that have been mutually estranged for so long will reap a bitter harvest," he said.
"The need to ensure that symbols and emblems are used to promote mutual respect rather than division is accepted. The challenge for all leaders across the island is to use their influence so that this generous vision is given real expression.
"I am encouraged by the recent steps that political and community leaders in Northern Ireland are taking and would urge them to continue their collaborative efforts," he added.