The only thing stopping an unregenerate man or woman from being a Hitler, Bin Laden, Stalin, Dahmer, or Manson is the restraining hand of the common grace of God.
Understand this. Before you came to faith in Christ, from your infancy, while you were not (and are not still) as depraved as you could be, you were nonetheless born a depraved hater of God. And everyone you know who does not know Jesus Christ as their Lord and Savior is, to this day and every day, regardless of how you feel about them or what you think about them, is a depraved hater of God with no inherent ability or desire to love and obey the Christ–the Son of the Living God.
To give your unregenerate friend or loved one the benefit of the doubt, to wishfully think that they will some way, somehow, apart from the drawing hand, effectual call, and irresistible grace of God turn away from their depraved love for sin (which they lap up like water and instinctively eat like a dog returning to feed on its vomit); may, in the end, result in a lack of urgency on your part to present them with the gospel of Jesus Christ–their only means of change and salvation.
Without an understanding of and appreciation for the sinfulness of sin and the depraved nature of every human being, you may errantly believe, on some level and at some time, your friends and loved ones have, in and of themselves, the ability to seek after God, the want for the forgiveness of God, the determination to turn toward God, and the desire to be reconciled with God. As a result, in word and deed–if not in thought, you may withhold the only thing that has the power of God to save–the gospel of Jesus Christ.
Your belief in your friends’ or loved ones’ goodness, common sense, and ability to repent on their own may leave you waiting for the day they choose God, as they perish in their sin. They will leave this world as they entered it–naked, clothed only in the filth of their evil, wretched, depraved, and sinful flesh. You may hope, as you look at their casket, they came to their senses on their own and repented as an outworking of their own will before they died, to ameliorate your sense of guilt for not sharing the gospel with them. You may trust they did something they were utterly unable to do–cooperate with God in their salvation. They will leave this world as they entered it–haters of God. And they will continue to hate God from their torturous place in Hell, for all eternity.
Understand the depravity and inability of all mankind, including yourself, to seek God apart from faith in and the love of Jesus Christ. Understand repentance and faith in Jesus Christ are gifts from God, not abilities of man. Understand the power to save men lies with God alone and His gospel. And you will evangelize your friends, loved ones, and the strangers you meet with a greater sense of urgency and with a deeper love for people and your God.