Luke 21 contrasts what lasts with what does not. The rich gave from their abundance, but a poor widow gave her whole living, two small coins. To human eyes her gift was tiny. To Jesus it was the greatest gift that day, because it showed total trust in God.
The temple was magnificent, adorned with beautiful stones and gifts. Yet Jesus said it would be thrown down, which happened in A.D. 70, about forty years later. He told His followers not to be led astray by false messiahs or terrified by wars, earthquakes and famines. They would face persecution and be brought before kings and governors. This would become an opportunity to testify. Jesus promised to give them a mouth and wisdom that their opponents could not resist.
Jesus then lifted their eyes to His return. The nations will be in distress, but the Son of Man will come in a cloud with power and great glory. Like a fig tree putting out leaves, the signs would show God's Kingdom is near. Heaven and earth will pass away, but Jesus' words will by no means pass away. So He warned His followers not to let their hearts be weighed down by worldly cares. Instead, watch and pray at all times. Each day Jesus taught in the temple, and at night He stayed on the Mount of Olives.