Our Savior Himself sets some necessary ground rules regarding understanding prophecy. He gets the timing of His return out of the way first: No one knows but the Father, not even Himself! So that should not be an issue with us—we should not worry about it or even be eager to figure it out, as it is a futile task, a time-waster. We will never be right, and it is unverifiable until it happens. Besides, most importantly, doing so provides little-to-no spiritual benefit.
What, then, are we to do? “Take heed, watch, and pray.” Because we do not know when He will return (notice He uses the more general “time” in verse 33, not just the specific day and hour), we must be ready for His return constantly. We do this by taking heed and watching.
“Take heed” is Greek blepete, which means “to notice carefully,” “to be ready to learn,” “to pay attention,” “to be prepared to respond appropriately.” The word-picture within it is a runner on a starting line who hears, “Ready. Get set. . . ,” and is poised to explode out of his stance as soon as the gun fires.
“Watch” is Greek agrypneite, which means “to keep oneself awake,” “to remain alert,” “to be sleepless,” “to be on the lookout,” “to be vigilant,” “to be on watch [duty].” The obvious illustration is a guard standing watch, keeping himself awake and alert to notice anyone approaching.
These commands are modified by “pray,” which implies being in constant communication with God. This modification suggests that our taking heed and watching are spiritual, not physical. The parallel verse in Luke 21:36 says explicitly that our watching and praying are focused on being counted worthy to escape the dangers of the end times and to stand before Christ.
That is how true Christians will be prepared for the Master's return—and for the Tribulation and the Day of the Lord, for that matter: by being diligent in keeping themselves on the straight and narrow path to God's Kingdom. This advice is the essence of Jesus' three parables in Matthew 25: We are not to sleep but to keep our lamps full of oil, faithfully use our talents for growth, and serve the brethren as we wait for the coming of our Savior.
Even so, Jesus also gives us signs of His coming so we will know when our redemption draws near. These prophetic guideposts are necessary to motivate us to trust Him and endure to the end.
In Matthew 24:3-8, Jesus lays out the first four seals of Revelation 6, but He twice emphasizes that these kinds of things will happen almost as a matter of course. He says, “All these things must come to pass, but the end is not yet” (verse 6), and “All these are the beginning of sorrows” (verse 8). As such, they do not indicate that the end is imminent. At best, these sorts of events mark the beginning of the end. Of course, religious deception, wars, famines, pestilences, and earthquakes have been happening all along, from before Jesus spoke this prophecy up until modern times. Their value in assessing how close we are to the end lies in their frequency and intensity.