In Jain Dharma, sincere repentance, confession, and firm resolution not to repeat the act are very important. They help in paring down the intensity of the karma and in purifying the mind.

But it is not correct to think that the effect is simply erased just by feeling guilt once. In Jainism, purification happens through:

• Alochana — honest confession of the fault
• Pratikraman — repentance and turning away from the wrong
• Pratyakhyan — a firm vow not to repeat it
• Careful conduct — avoiding the causes and situations that lead to it
• Self-restraint — as much as possible for a layperson

For a shrāvak / shrāvikā (layperson), if the act was done, then the right way is:

1. Accept the mistake without excuses
2. Feel true remorse
3. Ask for forgiveness from the Guru, Bhagwan, and in your heart from all living beings
4. Take a strong vow not to repeat it
5. Avoid the means, habits, and company that lead to it
6. Increase svādhyāya, pratikraman, and vrat-like discipline

So, yes, sincere repentance and confession are spiritually powerful and necessary, but in Jain view the real cleansing comes when repentance is joined with non-repetition and restraint.

A simple Jain understanding is:

• Past fault cannot be changed
• Present repentance can purify the future
• Repeated carelessness keeps bondage alive
• Sincere restraint weakens karma

If you want the most direct Jain answer: True repentance helps greatly, but one should not assume the sin is fully cleared unless there is genuine alochana, pratikraman, and determined stoppage of the fault.