As was common practice, before embarking on its mission, the Lasting Damage had transmitted a copy of its Mind State to another vessel. After its presumed destruction, this Mind State was embedded within a new GSV and it continued to participate in the conflict.
However, against all odds the original Lasting Damage had managed to survive, its Mind having escaped in a smaller vessel. It deliberately waited before trying to return to Culture space to avoid detection, and its survival was not known for some time. Upon its return, its successor renamed itself Lasting Damage II, and it took up the name Lasting Damage I. They became part of the same fleet, and fought together for most of the Idiran-Culture War.
Towards the end of the conflict both the Lasting Damage I and II were involved in the Twin Novae Battle. Before this battle the two Lasting Damages exchanged Mind states. During the battle the Lasting Damage II was destroyed. Afterward, the Lasting Damage I merged its mind state with that of its successor and concealed details of which of the two vessels was actually destroyed.
Significantly, at some point during the conflict, the Lasting Damage was tasked with the destruction of an orbital. This was done despite the fact that a number of people were still (willingly) on the orbital. This action deeply affected the Lasting Damage's emotional outlook on war and death.
As all citizens of the Culture (biological or artificial) are effectively immortal, choosing death at some point is relatively commonplace (though not so much with Minds). The choice to suicide is usually made after one feels that one has either lived one's life to the fullest, or has experienced something after which continued life would be too much of an effort.