When booking train tickets, regret refers to a status that may appear when trying to book a train ticket for a busy route. This happens when the IRCTC reservation system cant accept new booking requests for a train because it has exceeded the waitlist capacity for a given date. This may occur if you are booking trains very close to the actual date of a journey, especially before big festivals like Diwali, Holi, Ganesh Chaturthi, Chhath Puja, etc. Confirmed tickets for such periods are booked well in advance, and the waitlist can also be close to full. In such cases, your booking request may not be accepted, and you might see ‘REGRET’ as your train reservation status. The regret status means that no more tickets can be issued for that train, and waiting list tickets will not be confirmed. However, this status only applies to the general quota, and not to the Tatkal quota.