This is one of the most difficult and debated chapters in Scripture. Jesus speaks about the destruction of the temple, His second coming, the end of the age, the Great Tribulation, and how we are to prepare ourselves for these events. This is an area we should examine closely and seek to understand the Lord's words, but we should hold our conclusions with humility.
For me, the most important lesson of this chapter is not identifying the perfect prophetic timeline. It is listening to what Jesus repeatedly tells His disciples to do: don't be misled, don't be afraid, don't led your love grow cold, preach the gospel, and be ready.
Some of Jesus' words point clearly to the destruction of the Temple and of the Holy City of Jerusalem in AD 70, such as "Truly I say to you, not one stone here will be left upon another, which will not be torn down" (v. 2), but other portions seem to anticipate a future tribulation "such as has not occurred since the beginning of the world until now, nor ever will" (v. 21) and His second coming. There are challenging verses for both futurists and those who see most of the chapter as already fulfilled. Rather than allowing those difficulties to divide us, they should remind us that God's plans are sometimes fulfilled in ways we don't expect.
Consider the first advent of Jesus and the Messianic expectations held by the Jewish people. They rightly expected Elijah to come first, but who was able to predict the coming of Elijah would be in the person of John the Baptist? And who was able to predict it would not be the person of Elijah but the Spirit and Power of Elijah that would arrive as the forerunner to our Lord?
Now before you accuse me of being a fence sitter and start to call me Switzerland, I do hold to a pre-tribulation, pre-millennial view, however, I am very cautious about how zealous I proclaim this view and how rigid I allow my heart to be toward any alternatives God may surprise me with. It's tempting to force every difficulty into a system and and feel the need to explain away some verses while over emphasizing others. Remember, God's prophetic purposes have sometimes unfolded differently than His people expected. And these people aren't just anyone, they are some of the most faithful, dedicated, believers in the history of the world. People like Peter, James, and John. Humans are flawed. Thankfully we serve a God who doesn't rely on our ability to craft a perfect theological system and neatly arrange His Holy Scripture into said system.
Jesus, instead of telling His disciples to calculate dates and become consumed with prophetic speculation, tells them to be discerning, courageous, not fearful, not spiritually cold, and ready for His return.
The ultimate purpose of prophecy is not merely to help us understand the future, but to help us know the One who holds the future. Whatever our conclusions about the precise chronology, Christ's command remains the same: "Therefore, be on the alert." (v. 42).