According to Islamic belief the mundane existence is not the only existence. The Qur'an reminds "Everybody is going to die except God" Again it says "when the appointed time comes it does not come a minute ealier or a minute later" the prophet tradition says "this world is like an agricultural farm for the next world" i.e whatever you are sowing here, you will reap there.
The belief in life after death serves as a deterent and prevents people from entertaining any sense of complacency or a feeling of impunity. The Qur'an further says "Oh mankind, fear your Lord and dread a day (of judment) whereas no father shall atone for his son, and no son shall atone for his father at all. Verily the promise of Allah is true. Let not the life of the world beguile you and let not the great beguiler (devil) beguile in regard to Allah (Surah 31 verse 33).
In Islam, the death is not the end of life. Another kind of life will begin for a man after his death. One the Day of judgement, the good-doers will be rewarded and evil-doers will be punished. The blessed, the God fearing men and wome, the humble and charitable, the forgiving those who have suffered and were persecuted for the sake of Allah and His prophets, those who have fought in the way of Allah, will be asked to enter paradise. The paradise is the abode of peace in which there are abiding mansions.
Those who will enter paradise will have no worries and prolems and they will live they will live there by flowing rivers, prasing Allah, day and night, reclining on silken couches, enjoying heavenly food and drink. Above all they will be able to see the beatific Vision.
But those who are unbelieving, the covetous, the worshippers of deities and not One Allah, shall be cast into the Fire of Hell, to abide therein for ever, with no release from its torments, fed with the bitterest fruits and boiling water.