Fear alone persuades us to take precautions against falling prey to certain things. Until we are not afraid of something we do not take measures to protect ourselves from it. Same is for Islam. How can our Namaz be filled with khush'u and khuz'u when we don't fear Allaah Ta'ala in the real manner. How can we pause even for a second while backbiting;to consider that its gunah or slandering or adultery when we don't fear the fire of Hell! Fear is important to alter one's behavior/attitude. When a huge fire is burning what sane person would dare to go near it? The fear of its huge flames will not allow us to take a single step towards it.
In the same way, fear of Allah, Akhrah, the day of judgement, accountability and punishment is important to stop us from committing sins. When we are in a classroom we do not usually talk or misbehave because we fear that we'll be expelled from the class, then why don't we pause when we are lying, listening to music? Are we so fearless of Hell? Or do we think that we'll not be thrown into it by committing these sins? Or the most dangerous thing; we don't believe in it like it is to be believed? The way in which Allah has explained its intensity and nature should be enough to make our skin crawl with fear and to change our course of action in a more acceptable(to Allah) way.
Fear the day when it'll be brought into our visibility. There will be no escape from it and no going back to alter the condition. People will scream in bloodcurdling voices yet there will be no mercy that day. Allah forbid, non-believers will be thrown into it. May he bless us with Noor-Hidayah and save us from Hell. [Ameen]