The regeneration is a process that Time Lords go through to renew themselves physically and often mentally as well. The regeneration is a mean of dealing with illnesses, old age or injuries that threaten a Time Lord’s life; thus, to prevent their death, the old body regenerates into a new, healthy one. Although Time Lords remain essentially the same person throughout their regenerations, their personalities can be affected. According to the Doctor, regeneration is a painful process, and a Time Lord can suffer some negative side-effects for a brief period of time after he regenerates, such as confusion, erratic behaviour, extended periods of unconsciousness, or memory loss. Even though the regeneration process can be delayed for a short period of time, if prevented, leads to certain death.