In Canto III of the Inferno, Virgil leads Dante to the gate of Hell, where they read the infamous inscription sometimes translated as “Abandon all hope, you who enter here.” Dante comments that the inscription, which also warns them that they are about to pass into a place where God punishes lost souls with eternal torment, is a bit intimidating. Virgil then advises Dante to leave behind any doubts or fears he has about what he is about to see. If he is to learn from this journey, he must have faith and accept the suffering he observes as divine justice. Virgil offers Dante his hand, which Dante finds reassuring, and the two pass through the gate and into Hell.
In Dante's classic, The Divine Comedy, there are three parts to the entire work: Inferno, Purgatory and Paradise.
The question at hand is answered in Inferno, Canto 3. As Dante and Virgil, his guide on this fearfully wonderful quest, arrive at Hell they discover a gate on which is written -
"To enter through the lost city, go through me. Through me you go to meet a suffering unceasing and eternal. You will be with people who, through me, lost everything. My maker, moved by justice, lives above. Through Him, The Holy Power, I was made - made by the height of wisdom and of first love, whose laws all those in here once disobeyed. From now on every day feels like your last forever, let that be your greatest fear. Your future now is to forget the past. Forget your hopes, they were what brought you here."
These lines introduce several ideas, such as the fact that this place was not created by the Devil but by God, not for the purposes of evil but because He was "moved by justice" and "the height of wisdom." Regrets and sorrows, which are perhaps our greatest fears in life, are revealed to be what haunts us after death.
As they prepare to enter through the gate so that their quest may continue, Virgil does indeed have advice for his companion:
"Here you must renounce your slightest doubt and kill your every weakness. Leave behind all thoughts of safety first or be shut out..."
In pursuing the journey on which Dante finds himself, he must believe. He must be willing to put first and foremost a trust in God that what he is about to see is right, and he must overcome the natural tendency to put yourself first: a task that few are able to accomplish.