'Careful' in the Bible

Tell him, "Be careful, be calm, don't be afraid, and don't lose heart because of these two smoldering stumps of torches, that is, because of the fierce anger of Rezin, from Aram, and Remaliah's son.

Be careful not to let Hezekiah mislead you when he says, "The LORD will save us." Has any god of any nation ever delivered his country from the king of Assyria?