One noteworthy thing about Scripture is that it doesn't speak as if only the saved are supposed to understand it. It is filled with if/else statements, and makes it quite clear that any one of its readers may fall on the side of "else". Consider the following example:
"Or do you despise the riches of His goodness, forbearance, and longsuffering, not knowing that the goodness of God leads you to repentance? But in accordance with your hardness and your impenitent heart you are treasuring up for yourself wrath in the day of wrath and revelation of the righteous judgment of God, who “will render to each one according to his deeds”:" (Romans 2:4-6).
Who is this speaking to? The answer, especially when we expand our reading to verse 10, is everyone. It's a clear warning: God's kindness is not to be taken for granted. It is designed for one purpose, that being to lead us to repentance. God could, and would be quite within his rights to destroy us the moment sin entered our hearts for the very first time. Instead, He suspends His wrath, giving us time to repent, but also not actively preventing us from committing more sin.
This means we are faced with a choice: Make good use of His patience and repent, as is His purpose for extending such grace to us, or make a mockery of God by continuing in our sin, by which we are treasuring up for ourselves wrath in the day of God's judgement.
Is this danger real? We must answer yes. Even if we firmly believe God's grace is totally irresistible, and therefore everyone to whom He extends it was always going to escape the fires of Hell, we must affirm that they were heading for those fires.
But here's where it gets difficult for the Calvinist. As shown by this passage, the same kindness that leads the elect to repentance is extended to the impenitent, who will receive the very wrath they have stored up for themselves. But if that kindness is designed to lead us to repentance, it is also designed to lead them to repentance. In other words, God's grace is extended to all, can be effective for all, and can be resisted by all. That's Total Depravity (in the Calvinist sense), Limited Atonement, and Irresistible Grace, knocked out by 6 verses.
Total Depravity is knocked out because the entire passage assumes that man is able to respond to God's goodness, even in a way that urges us to do so. Limited Atonement is knocked out because there is no distinction drawn here between the elect, who will repent, and the wicked, who will not. Irresistible Grace is knocked out because it tells us plainly, not only will people resist, but the very audience of Romans could be among them! The goodness of God leads me to repentance, but I could refuse to repent. The goodness of God leads you to repentance, you could still store up wrath for yourself. The goodness of God leads every single person who has ever read the book of Romans to repentance, yet any single one of them may forever forego the privilege.
With this in mind, it seems logical to discard Calvinism. This being but one example, nowhere in Scripture draws any distinction between whom God wills to be saved, and whom God actually will save. Indeed, His word expressly tells us He wills for all men to be saved and come to the knowledge of the truth (1 Timothy 2:1-4). Let us therefore assume He means what He says, and ensure we are among the penitent.