Hashem promises, says the Talmud, whenever His children are in need of heaven's mercy "a covenant sealed with The 13 Attributes (of Hashem, that when actualized) they never return empty," i.e. without achieving His Divine mercy! And yet do we not see times when we in fact call out His 13 Attributes and are not answered in kind?!
Certainly before the great Day of Judgment, when we all need His compassion, it behooves us to know how to properly access for ourselves the awesome power of the 13 attributes, so that we might gain His Divine mercy and compassion and assure ourselves a positive outcome to the Yom HaDin!