Now I, like you, am willing to give up on things. I demand proof that you have something to offer before I'm willing to invest in the relationship with a book. Only very rarely do I violate this practice -- if something gets a ton of a buzz I might push through when otherwise I'd quit.
I wonder if we're better or worse off. Certainly we're different readers now, and probably writers.
I'm in exactly the same situation and do the same thing. There's nothing that reminds me more of my mortality than looking at my (digital) library of books that I have yet to read. It's obvious now that unless I make it very big I won't ever have the time to read all of them so it's very important that I do not waste time reading books that aren't worth it (technical books are mostly exempted from this though). Like you say it's a hard habit but it's the most efficient thing you can do since time is such a scarce commodity and books are dime a dozen these days.