We do

because theres a constant struggle between good [i.e. faith/emaan] and bad [disbelief/kufr] throughout mankind and the times. When Al-Dajjaal [the imposter] comes, he will pretend to be a prophet, and gradually lead people to believe that he is God.
Allaah will allow him to do many miracles, this is a trial for mankind - but with a long hard trial, Allaah will send Eesa ibn Maryam [Jesus son of Mary (peace be upon them)] to fight the anti-christ and he will slay him. After this there will be bliss and Allaah will allow the treasures of the earth to come out, this will be really near to the end of time. The Messiah, Jesus son of Mary will marry and live upto a certain time period and then corruption will spread once again on the earth.
The trumpet will be blown and everything will be destroyed, except the Lord, Most High, our Creator. 'Who is the king today?' He will say.
When Allaah wills, the angel who blew the trumpet will come back to life and blow the trumpet once again by the will of Allaah. The graves will be overthrown and mankind will run like scattered moths, in a state of shock. This is the day when the evil ones will be repayed for their actions, and the good will be rewarded for all that they did. Allaah will not treat a soul unjustly in any way. It's the day of which theres no doubt.