Beware that no one leads you astray.

Mark 13:1-8

Context
Apocalypses - stories of people being taken up to the skies and being told of the imminent end of the world - were developed in Jewish literature in the two centuries before Christ and were popular in Jesus' day. The Biblical book of Revelation is an example of an apocalypse. Portions of Mark 13 are sometimes called "the little apocalypse".
The Temple was destroyed by Rome in the year 70. Most scholars believe that the book of Mark was written shortly before or after the destruction of the Temple.
In the gospel, Jesus and his disciples have just entered Jerusalem. It's a few days before he is crucified.

Listening to the writer
The disciples are in awe of the Temple. For the poorer disciples, it may have been their first visit. The temple in Jesus' day was built by King Herod about 20 years before Jesus was born, and was definitely an imposing site. When the disciples say "what large stones," they weren't kidding - some were over 40 x 15 feet.
It's not clear what "all these things" are in verse 4. In the preceding context, it seems to be the destruction of the Temple, but from the following discussion, it seems to include the end of the world. (Some Jews might have equated the two, of course.) Regardless, the early Church believed that the end of the world was near.
Jesus names a handful of things that have happened throughout history - people claiming to be the Messiah (there have been false Messiahs for as long as the idea has been around), war, earthquakes, and famine - and says "don't be led astray".

Listening to God
It is easy to get caught up in awe at our present accomplishments. What recent human achievements do you find amazing? (I hope there are some. Genesis 1 lists us as God's greatest creation, after all - it's OK to be amazed at what God has done.)
Jesus reminds the disciples of the temporary nature of our creations. Are you finding some human creations to be taking priority over God, either as items of worship or of fear? (These need not be physical; I'm aware of the Democratic and Republican parties, which frighten me and can occupy too much of my thought, but will one day crumble.)
People are constantly predicting the end of the world. There is a whole branch of Christianity that focuses on interpreting the Biblical apocalypses and seeing signs of "the end times". Jesus says "Beware that no one leads you astray." How about you - do you need to change your focus?

Miscellaneous Meanderings
The rest of Mark 13 is fascinating reading. For the short version, just read verses 32 and 33. If you decide to study the rest, make sure you do so with several good commentaries at hand (Textweek has links). The chapter almost certainly has a complex history.

Dig deeper at TextWeek.