The Result pairs of types are all about identifying oppurtunities first and then choosing between them. I think this last thing is what smilingeyes means by "discarding". It was mainly the omission of the first part of the process, without which the latter part makes no sense whatsoever, that made me not recognize it. What I think the description doesn't do justice to is the fact that the discarding is done with a purpose. The discarding approach is the only way to make use of combinations of oppurtunities. You try to combine as many of them as you can, but there is always something that remains left out. In a sense, he only describes a fringe aspect of the process. It's probably the most visible part of the process, though. The "we can't include that oppurtunity without giving up a better combination" decision point is kind of like a goal that one tries to reach. An Negative/Result type who is very sure of himself can manifest that attitude for long times on end.

( A really important thing to realize about the socionics functions, in my opinion, is that the Static functions always work through and/or "on top of" the dynamic functions. This is how discarding oppurtunities follows up on finding oppurtunities, and how identifying obstacles (Negative/Process) is followed by manifesting optimism towards overcoming these (Positive/Process). )