The Talmud states that “if a person commits a sin and repeats it, it becomes to him as though it were permissible” (Yoma 86b).
Regarding repentance as well, there can be an equally dangerous predicament where someone is caught in a cycle of remorse and teshuva followed by a return to the sin, followed by remorse once again.
When a person does teshuva the first time, it makes an impression.
But when he does teshuva twice or five times for the same sin, teshuva becomes a meaningless procedure, one that can be repeated over and over again, while nothing actually changes.
–Rabbi Adin Steinsaltz