Multiple Attempts

Whenever a D&D character attempts to do anything, they roll a 20-sided die, add all relevant modifiers, and check to see if their total is higher or lower than the number that represents the difficulty of what they were trying to do. If their result is equal to or higher than the Difficulty number, then they succeed. If their total is lower, they fail. However, that only considers a single attempt. If time permits, they may make multiple attempts, making a separate roll and check for each attempt. That way, the character could succeed at something terribly difficult, or fail at something perfectly easy.

For example, my Barbarian D&D character, Krusk, is good at throwing axes. Throwing an ax requires Strength, and Krusk is incredibly strong, with a +5 Strength modifier. He is also Proficient with ax-like weapons (as well as almost all other types of weapons), so he gets to add his +3 proficiency bonus as well. If he was trying to hit an easy target, like a stump, the Difficulty of hitting that stump would probably be about 10, so Krusk would roll a d20, add his +5 Strength modifier and his +3 proficiency bonus, and if his total is 10 or more, he hits the stump. Between his Strength and his Proficiency, he's adding 8 to whatever number the d20 gives him. Any result of 2 or higher will give him a total of 10 or more, meaning that he's almost guaranteed to hit that stump.

Almost.

There is a chance (a 5% chance, to be precise) that he could roll a 1. One plus five plus three equals nine, which is not high enough to hit the stump. For every hundred times Krusk tries to hit that stump with a thrown ax, he is likely to fail an average of five times.

However, if Krusk tried to hit something difficult, like a small target at the top of a tree, the Difficulty will be much higher, maybe somewhere between 25 and 30. If the difficulty was exactly 28, Krusk would need to roll a 20 on the d20 in order to hit the target, which is just as unlikely as rolling a 1. Still, if he has enough axes, or if he keeps retrieving the axes he throws and misses with, he will eventually hit that target. It'll just take him an average of 20 attempts to do so.

I say all tis to illustrate the fact that, if we make enough attempts to do something, no matter what the odds are, both success and failure are inevitable. As long as there is any chance of success at all, and as long as we keep trying, we will eventually succeed. However, as long as there is even a chance of failing at something we do repeatedly, it is inevitable that we will fail at least a handful of times.

And there is something that we are almost constantly trying to do, where even a single failure could be spiritually fatal: resisting temptation.

Whenever we have to make a decision, Satan attempts to convince us to make the wrong decision, and we (hopefully) try to choose the right anyway. We probably often succeed at this, but as long as there is even the slightest chance that we might give in to temptation, Satan's persistence and repeated attempts will ultimately win at least once, and we will give in to temptation at least once. Considering any probability and given a near-infinite number of attempts, I can say with some certainty that every human being who has ever lived and how will ever live will fail, at least once, to resist the temptation to commit sin. The result is inescapable: Everyone will sin.

This might be why repentance was always part of God's plan. Elder Lynn G. Robbins said, "Repentance isn’t His backup plan in the event we might fail. Repentance is His plan, knowing that we will."

As we make repeated attempts to resist temptation, it's inevitable that we will fail from time to time, so we shouldn't berate ourselves too harshly when that happens. Instead, we should learn from that failure and try to decrease the odds of it happening again. I don't think we'll completely eliminate the possibility of failure, not in this life anyway, but we can improve our odds. And while we wrestle against Satan countless times each day, we can also turn to the Lord with similar frequency, asking for His guidance (which could add a +1d4 bonus to our skill checks) and for His forgiveness when our numbers don't quite add up.

God knows that we will need His forgiveness. He knows that, as long as we're human, there will always be a chance that we may fail. And He knows that, given the number of times we have to attempt to resist temptation, both success and failure are inevitable. God's not going to be too terribly upset if we fail from time to time. Perhaps we shouldn't judge ourselves too harshly for our inevitable failures either.