Mark 13 describes a sequence of events that is to take place before Jesus' return. Yes, Jesus is coming again, and will not delay! The time of these events, though horrific and tragic, are likened to birth-pangs, and shakings, before the coming of a new age, where Christ will return to rule and reign on the earth.
The events that can be most concerning to us is found in Mark 13:6, and 13:22: deception. False Christs and false prophets will present themselves, with signs and wonders, and deceive many, even the ones God has chosen for Himself!
The greatest threat to deception, may not be those false Christs, or false prophets, but it may be us. Jesus commands US to be on guard, stay constantly alert, and pray. We must consider that the perfect stage for deception to take place is when our heart is mixed, when the good of the world are mixed in with the perfect things of God (good is the enemy of the best), when our heart is mixed with the sacred and the profane. We must be vigilant to set ourselves apart - be holy.
May we pursue purity of heart, and not a mixed heart, for Jesus is returning for a pure bride. Be on guard, constantly alert, and pray. We will have no excuse, because Jesus warned us in advance!