Huuuuh, now that is difficult to say the least. I expected "moving on" from a girl you loved if dumped or something, which I could handle in a snap. I do not hold strong attachments in a majority of cases. However if I met the girl of my dreams so to speak and had married her or been with her for quite a few years (say five to ten for a reference) that... that would be a blow which would almost certainly break through the armor in the sense I usually do not give much of a damn about things.
That is not something I am at all certain I could bounce back from. Perhaps over time but I imagine it would be very difficult. Now if she were murdered? Oh boy... lets just say the person who did so better either be in jail already or dead because I cannot say I'd have any level of sanity left, especially if it was a brutal murder. Not that I would harm others, just this person and harm is mildly putting it.
All I know is I would never commit suicide, even in this depressing a scenario. I would live on, how I would be going forward, well there in lays something I never want to know.
Edit: Thinking about it further, I do believe I could carry on with life, especially if we had children. However I probably would not date again.