I've heard some say that nothing can separate us from God, except ourselves. Until we die, we still can reject God and lose our salvation. We're really not certainly saved until we are dead. Huh?

Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? As it is written:

"For Your sake we are killed all day long;
We are accounted as sheep for the slaughter."

Yet in all these things we are more than conquerors through Him who loved us.
Romans 8:35-37

It's a temptation when tribulation, distress, persecution, famine, nakedness, peril, or sword afflict us to think that God is judging us. We think his wrath is on us. He's forsaken us. Or we think it will never end.

But Paul says that whatever happens, we must stand firm in faith -- the faith that once God embraces you in love, He never lets you go. I really think that the "depravity" issue is what confuses people on this. Because if you've got a firm grasp that you are indeed sinful and guilty, and that God is infinitely holy and righteous and just. You can't turn His heart. You can only turn His stomach. But, in spite of that, He choses to love you. Since nothing you can do would make Him love you, there's nothing to make Him stop loving you.

"But what if I did something really bad?" Have you ever done anything good? Did you think you had done enough good to swing the balance? No? Ever have a lustful thought? Let's estimate that you had one once every couple days or so. Let's take that out to 164 thoughts per year. God sees every one of those as adultery. Now consider how you'd feel about your spouse committing adultery 164 times this year. After five years, that's 820 times. Have you done anything really bad yet? We don't see the sinfulness of our sin.

If you were God, and really saw your sin, you would never save you. But God is infinitely merciful and just. He is infinitely merciful that he would take an 820-time adulterer and save him. He's infinitely just in that the full wrath and curse of God for those 820 acts of adultery was placed on Jesus. And He did that almost 2,000 years ago, which, in case you hadn't notice, was before you were ever born. You hadn't committed any sins at that point. This was even before you were conceived in sin (Psalm 51:5). So every one of your sins was future. There is no sin you can commit that was not already covered by Jesus. (I'm speaking to believers, of course).

What about the tribulation, distress, persecution, etc.? Of course, as the author of Hebrews says:

And you have forgotten the exhortation which speaks to you as to sons:

"My son, do not despise the chastening of the LORD,
Nor be discouraged when you are rebuked by Him;
For whom the LORD loves He chastens,
And scourges every son whom He receives."

It is for discipline that you endure; God deals with you as with sons; for what son is there whom a father does not chasten? But if you are without chastening, of which all have become partakers, then you are illegitimate and not sons.
Hebrews 12:5-8

Don't be ungrateful! The Lord is chastening you because He loves you. He is perfecting you. When you are chastened, your first thought should be that God loves you.

Be encouraged:

And I will make an everlasting covenant with them, that I will not turn away from doing them good; but I will put My fear in their hearts so that they will not depart from Me.
Jeremiah 32:40

Most assuredly, I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life.
John 5:24

And I give them eternal life, and they shall never perish; neither shall anyone snatch them out of My hand.
John 10:28

being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ;
Philippians 1:6

For God did not appoint us to wrath, but to obtain salvation through our Lord Jesus Christ, who died for us, that whether we wake or sleep, we should live together with Him.
1 Thessalonians 5:9, 10

Now may the God of peace Himself sanctify you completely; and may your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ. He who calls you is faithful, who also will do it.
1 Thessalonians 5:23, 24

But the Lord is faithful, who will establish you and guard you from the evil one.
2 Thessalonians 3:3

Blessed be the God and Father of our Lord Jesus Christ, who according to His abundant mercy has begotten us again to a living hope through the resurrection of Jesus Christ from the dead, to an inheritance incorruptible and undefiled and that does not fade away, reserved in heaven for you, who are kept by the power of God through faith for salvation ready to be revealed in the last time.
1 Peter 1:3-5

Though now you do not see Him, yet believing, you rejoice with joy inexpressible and full of glory, receiving the end of your faith--the salvation of your souls.
1 Peter 1:8b, 9

Since JD brought it up and I never really covered it:

Question #7: Could Judas have refused to betray Jesus?