Wow. What a reversal of roles. Instead of Clark deciding unilaterally that they can't be together (for a really dumb reason), Lois decides they can't be together (for a less dumb but equally selfish reason). I like the setup, and I love the insight into Lois's thinking.
And her seeming selflessness is actually selfishness. She's trying to protect herself from the hurt of knowing that she will disappoint Clark if they get too close, so she's putting a stop to it (she thinks!) by playing the "I'm broken and you can't fix me" card. It seems that this Lois isn't much different from the self-centered Mad Dog in season 1 after all.
Oh, you simply must give us the next scene. Does Clark chase her, or is he rooted to the spot by her revelation? Does she lose her resolve the next time Clark comes by her place with a Lethal Weapon video and a half-gallon of chocolate ice cream (Ben and Jerry's, maybe?) and a carton of double-fudge crunch bars?
This is too good to be a stand-alone. We, your hungry readers, eagerly await the next term of estrangement. In this case, once is definitely NOT enough!