This passage from Mark is a bit heavy. It's easy to get mired up in all the imagery, the desecration and the people fleeing for their lives. (Augustine thought that the nursing mother was symbolism for those who cling to the world instead of keeping their focus on the Kingdom, so there's definitely some possibility for metaphor running throughout.) The thing that we can definitely take away is this: Jesus asks he followers to be focused. In the verse directly preceding, he had said, "the one who endures to the very end will be saved," and he comes back around to that idea today with the idea of keeping watch. Indeed we should. There is a lot to distract us from our Kingdom message, but we have the Spirit to remind us where our true citizenship lies.