There are quite a number of interesting things to consider in Jesus' instructions here. First, this is not instruction given generally to the public, but rather it was directly to His disciples. Second, He says that we should know from the signs given that His return is near. Our predictions may not be specifically accurate, but at least in the ballpark—near. Third, He emphasizes the element of surprise, even terrifying surprise. The impression is that the world will be taken completely by surprise. Fourth, the overall point of this instruction is that by being alert to the signs and taking advantage of them, we should be ready. The fifth is a final warning in verse 44, because He feared that even the attention, the alertness of His disciples, would be threatened: "Therefore be you also ready: for in such an hour as you think not the Son of man comes."
Are we getting anxious about Christ's return? I do not mean anxious in a sense of being fearful, but anxious in terms of seeing it come to pass. First, because things are getting so bad one wonders at times whether it can get much worse, and yet we know that it can. Second, as a result of the pressures of enduring life, there is some measure of concerned anxiety because the end seems to be taking so long to come to pass. We are undoubtedly in "the time of the end," but at the same time we feel that we have been on the gun lap a very long time.
Part of our anticipation exists because we have had it drilled in our minds to watch for certain events to happen. Sometimes it looks as though those events indeed are coming to pass, and right now some of the more important events we had drilled into our minds just are not happening in a clearly visible way. If they are, they are being worked out in a way that we are not prepared for, and therefore probably do not see.
Jesus meant this admonition in the sense of a soldier on guard duty, alert to what is going on around him, and so watch we do! But what if our point of view—the perspective we are looking from—is not correct? We might be alert, diligently and sincerely looking in that direction, but at best, we are only getting a part of the picture. We might be likened to a soldier on guard duty who is alert, but looking in the wrong direction, and so the enemy sneaks up from a blind spot and surprises him, despite him looking intensely in a particular direction.