You seem pretty upset.  I've been in this place 
myself;  I take my sales commitments pretty 
seriously, and I get pretty bent when something 
goes wrong and my buyer is unhappy.

Here's what I do....

As you said "Money is just money", whereas self-
doubt and guilt is forever.

Go off into a corner by yourself for while, and 
sit and think.  Think through to what would make 
you feel better, what would make you feel like a 
good person.

Think though to what you might take as an action, 
that you will tell your grandchildren about 
someday that will be a good lesson to them, and 
will make you feel happy about what you did in 50 
years when you tell your grandchildren about it.

Then do that.

I've never regretted taking this approach.