How long does it take a man to get over failing to protect a loved one from harm?

I've heard several cases where this has happened and many times he won't let it go even when it wasn't his fault. It seems he's not only impacted but so is his ego, pride too. We get affected too but it seems the guy takes it even much more personal.

For instance my friend is one case. Even though he finally came to terms with the outcome, certain times he still has some guilt over it. He got beaten and he couldn't do nothing when his younger sister got raped.

Seriously, if the guy couldn't protect a loved one from harm... how long does it take him to finally move on from that? To fully recover and no longer think so badly of himself?
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He seemed to be more impacted than his sister. The girl already received help long ago and was able to move on from that terrible event. She never once blamed him. Meanwhile my friend took much longer to recover. He used to think low of himself. He developed low self-esteem and low confidence at the time.
How long does it take a man to get over failing to protect a loved one from harm?
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