The biggest obstacle to change is the belief that we cannot change. It is the perfect example of a self-fulfilling prophecy.
The following is brought in the name of the Shelah HaKadosh:
Some overly pious people [who wish to discourage tumah] are very stringent, asserting that it is impossible to repair a sin involving kedushah ...
These individuals increase the number of sinners in Klal Yisrael by discouraging them from returning to beneath the Shechinah’s wings. For upon hearing this, the sinner tells himself that there is no repentance in any case. Once I am lost, I’m gone forever ...
A recent social experiment demonstrates this truism.
A group of students were read a passage from Francis Crick, the famous molecular biologist, who denied the existence of free will. In this article Crick asserts that free will is a quaint old notion no longer taken seriously by intellectuals, especially not psychologists and neuroscientists. Afterward, when compared with a control group that read a different passage (also from Crick, but on a different topic) the former group expressed more skepticism about free will - and promptly cut themselves some moral slack while taking a math test. Asked to solve a series of arithmetic problems in a computerized quiz, they cheated by getting the answers through a glitch in the computer that they’d been asked not to exploit. The supposed glitch, of course, had been put there as a temptation by the researchers.
In a follow-up experiment, the psychologists gave another test in which people were promised $1 for every correct answer - and they could compute their own scores. Just as the researchers feared, people were more likely to cheat after being exposed beforehand to arguments against free will.
When we lose sight of the fact that we really do have a choice - then and only then have we lost the battle.
In fact, this mindset played a pivotal role in Acher’s downfall. To recount briefly: There was once a Tanna named Elisha ben Avuyah. He was R’ Meir’s rebbi and is quoted in a Mishnah. Sadly, he eventually became a heretic, after which Chazal began to refer to him as “Acher” - the Other. One Yom Kippur he brazenly
mounted his horse and rode to the vicinity of the Beis HaMikdash where he heard a Heavenly voice stating, “Return, you rebellious children - except for Acher.” Upon hearing this, he said, “Since I can never repent, let me go and enjoy this world.” He despaired of changing and as they say, just “threw in the towel.” In fact, says the Shelah, he was mistaken; the Heavenly voice merely was not inviting him back; but he still could have changed on his own.
But even this voice was for Acher only. As for the rest of us, Hashem is actively calling out to us, encouraging us to change.
He is there to help us along, as we say in Neilah: You extend a hand to repentant sinners. You draw them back to You.
It is like the well-known scenario: A person rushing to make a train enters the platform just as the doors close and the train begins to pull away. In desperation, he races alongside the train as it slowly picks up speed; a passenger standing in the open caboose at the rear of the train extends his hand toward him. He reaches for it; they lock hands and the passenger hauls the man onto the train.
Hashem extends His hand and hauls us in, as long as we reach out toward Him.
Every Jew can change. Hashem not only waits with open arms; He reaches out toward us! We are never forsaken.