A lot happens in this very short writing in Mark. What we are finding is that when reading through this Gospel in order, we are realizing just how out of order things are when we hear the Gospel in church. For instance, we typically associate Jesus triumphant entry into Jerusalem with Passion Sunday, where Jesus is suddenly turned upon and set into the Passion readings. We hear both readings in the same Mass, and tend to associate them, however, quite a bit happens in between with no definite timeline given.
In Mark 11, Jesus enters into Jerusalem for the first time in this Gospel. This entry is the one we typically hear on Palm Sunday. He proceeds to go to the temple and flip out on the people who have turned the temple into a marketplace, clearly upset that a place of worship was being used for profitable means. This was the first instance in Jerusalem that caused the Jewish leaders to plot against him. they were upset that he was shaking up their racket and teaching with authority as an outsider from the temple. This was the first instance where they tried to catch him in blasphemy, asking "on whose authority to you say these things?" Jesus, knowing they have asked a question that cannot be answered in anyway that wouldn't be seen as blasphemy responds with a riddle about John the Baptist that they cannot answer for similar reasons. This is the first of many times that Jesus uses his wit to avoid being judged.
This creates a question: Why would Jesus not come out and say that he was who he was? Obviously, if he did, they would take it as a case to prosecute him, but eventually, in Mark 14, after false testimonies against him, Jesus finally gives in and admits to being Christ, giving the leaders of the community reason to prosecute. Again I ask, why did he put it off if he was going to eventually give in any way? Why? The clear reason seems to be "in fulfillment of the scriptures." It needs to happen at a certain time in a certain way for prophesy to be fulfilled. More than that though, I think Jesus did not want to go through it. This becomes blatantly obvious in Mark 14 when he is praying in the garden asking God to let him live. Remember, Jesus was a human, with human emotions. It can't be easy willingly allowing yourself to die when you know you could easily get out of it. After all, if Jesus was human, he too was granted free will.
Now that we've connected chapters 11 and 14, lets take a look at what goes on in chapters 12-13.
Mark 12: This chapter is a series of parables, all being used to refute those who are trying to catch Jesus unawares in an effort to persecute him. The Pharisees, Herodians, Sadducees and scribes all make efforts to catch Jesus in blasphemy, trying to prove that they are smarter than him. In every occasion though, Jesus flips their words around not just to get out of a jam, but to teach them a lesson about God, the kingdom of heaven, or any number of things that they seem to have forgotten about.
Mark 13: Perhaps the most engaging part of this section, Jesus shares with a select few of his disciples details of the end times. The most intriguing part being the last verse: Mark 13: 37: "And what I say unto you I say unto all, Watch." He is informing us that there is never a time to let our guards down. There is never a time that we can slack off and be bad people. There is never a time to doubt. There is never a time to give up on living a good life. Why? Because we never know when the end is coming, and we don't want to be slacking off when it does.
The usual spin on the preceding is that we should be good because God might catch us slacking off. I feel that it is more of a warning not to let evil into the world. After all that we have read in Isaiah about bad things happening to people as a result of their own bad doings, it isn't a far cry to associate the end of the world similarly. Especially in a time in this world when there is so much wealth and so many distractions in front of us, keeping us from paying attention (work, technology, mass media, etc.) to what is truly important. The end won't come when we least expect it, but rather when we have stopped watching for it because we are too distracted by creations of man. Remember, "And what I say unto you I say unto all, Watch."