Check out Auren's latest post, To Grow a Company, You Need to be Good at Killing Things.
Moving on from things that don't work was the hardest career lesson for me to learn. I always wanted things to work and assumed that "hard work" would make it better. (Corresponding lesson: hard work doesn't equal good work.)
I've seen the same lesson in tech, finance and retail. It might be as small as a marketing campaign that you worked months on or it might be as big as a business line that you've pinned your hopes on, but knowing when to move on from an investment is a key effective strategic planning.
And I'm going to start ending all my posts with a comic.