Jesus told His disciples to watch and pray so that they do not fall into temptation because the flesh is weak, though the spirit is willing (Matthew 26:41). The Apostle Peter writes that we need to be sober and watch unto prayer, because the end of all things is at hand (1 Peter 4:7). Those who do not watch are in for a surprise for Jesus shall come as a thief at an hour that is unknown (Revelation 3:3). Those who watch are not only those who do not fall prey to temptation but they are also blessed (Revelation 16:15). Only those who watch and pray always, may be accounted worthy to escape all the things that shall come to pass, and be able to stand before the Son of man (Luke 21:36).

As Christians, not only are we, to be on watch (guard) so that we do not fall to the schemes of the devil, but we are also to watch (gaze) for the coming of the Savior, Jesus Christ.

1 Thessalonians 5:6 (KJV)
6 Therefore let us not sleep, as do others; but let us watch and be sober.