if you planned a litter , did all the tests , and had a good sized litter for you to choose from
if you did not like any of the pups not in a way of hate but say after so many weeks
watching them grow and watching the movement etc etc  and you thought no not for me
would you keep one back anyway or just think it was not meant to be this time ?

If one of the pups didn't meet my criteria I wouldn't keep one just to justify the litter but I would also remember that some ugly ducklings can turn into beautiful swans and visa versa, 8 weeks can be too early to make that final decision.

If non of them appealed to me I wouldn't keep one.

I don't think I'd gel with it.

This happened to me - had a litter of 10 with even split bitches/dogs.  Wanted a bitch puppy to keep but none of them did it for me.  Had a friend down to look at them and she also said there wasn't one worth keeping as I wanted to show and breed on from her.  A very hard decision to make as it was this girls 2nd and final litter.  I often think what if I'd kept, would she have developed into a swan?...

You have to do what you think it right.  I did feel quite guilty about having a litter and a large one yet not keeping a puppy.  If you did take a chance and run it on, would you be able to sell it/part with it should it not come up to scratch?  I couldn't so made the decision to sell the pup early on.

I don't think any of us envy you making your decision.

It depends on how experienced you are at judging your lines too. 

Have you asked other experienced and successful breeder friends to help assess you litter?  Would this be possible?   Having others input can help enormously (as long as you trust them )   

I did this with my second litter as I found it difficult to choose between the only two bitches, it was a splitting hairs decision :-)

As it happened the people asked were also split between the two lol but it did help me make my decision :-)