Answer

If he sincerely repents, says “micchhami dukkadam,” and voluntarily takes a vow or does a tyag for some time, that is a good and meaningful first step in Jain Dharma.

But if the fault was serious and deliberate, then self-chosen tyag alone is usually not considered a complete prāyaścitta. It is helpful, but proper repentance should ideally be followed by guidance from a guru or experienced Jain guide.

Explanation

In Jain Dharma, the main thing is not just external punishment. The important points are:

• sincere alochana: honest confession to oneself and, when possible, to a qualified guide
• repentance: true remorse without justification
• pratikraman: turning back from the fault
• resolution: strong determination not to repeat it
• prāyaścitta: suitable atonement

So if someone says “micchhami dukkadam” from the heart, that is spiritually valuable. If he also takes a vow, such as:

• a temporary brahmacharya vow
• tyag of a comfort or indulgence
• extra samayik
• more recitation, prayer, or fasting

then that can help purify the mind and strengthen restraint.

However, the value of the tyag depends on sincerity and discipline. If it is done casually, it has less weight. If it is done with deep humility and real self-control, it becomes spiritually meaningful.

Spiritual Understanding

In Jain Dharma, the goal of penance is:

• cleansing the soul
• weakening passions
• rebuilding self-restraint
• preventing repetition of the fault

So the inner change is more important than the outward form.

A self-imposed vow is good when it is:

• realistic
• sincere
• not done for show
• supported by true repentance

But for a grave lapse, Jain tradition gives great importance to proper prāyaścitta, because the aim is not self-punishment, but correct purification.

Takeaway

So the answer is:

• Yes, sincere repentance, micchhami dukkadam, and voluntary tyag are spiritually good.
• No, they may not fully replace proper prāyaścitta in a serious deliberate fault.
• The safest Jain approach is: repent sincerely, do pratikraman, take a meaningful vow, and seek proper guidance.

If you want, I can also explain what is sufficient for a small lapse versus a serious lapse in simple Jain terms.