Mar 2:20But the days will come, when the bridegroom shall be taken away from them, and then shall they fast in those days.

Christ uses fasting, going without eating, and mourning the loss of someone as closely connected ideas. This is seen more clearly in the verse related to this in Mat 9:15 (discussed here). The the physical loss of giving up food is connected with the emotional loss of losing a relationship. Happiness depends on our relationships and our physical and mental well-being. All three parts of life are closely connected.

All three parts of life are also temporary because much is hidden from us in this life. Though Christ promises to be with us on all days (Mat 28:20), he also recognizes that he is not physically apparent (Mat 26:11) as he is in life. To be alive is to have nothing permanently: not satisfaction from hunger or satisfaction from our relationships. Even the most perfect relationships are marked by absences.

Notice that Christ does not refer to people moving through time, but the times (in this case the "days") as moving toward us and then away from us. We are like God in the sense that we are in essence timeless and eternal, but we are placed in the path of time, in lives of temporary things: our bodies, our thoughts, and our relationships are all temporary. Our actions and choices are temporary. All of these things move, but at our core we are still, centered, unmoving. We experience life as a parade of days. It is the stream we are lost in, the water that we must be pulled from in order to wake up and turn ourselves around.

"Will come" is from erchomai, (erchomai) which means "to start," "to set out," "to arrive at," "to come" and "to go." It generally refers to any kind of motion. It is a little like we use the phrase "he is on his way," which can mean either that he is coming or going with no direct reference to coming to or going from the position of the speaker.

"Shall be taken" is apairô (apairo), which means "to lead off," "to lift off," "to carry off," "to remove," "to get rid of," and "to lead away."