Why does everything have a last time?

Dr. Y, one of my favorite profs was on the stage in a yellow Tee, looking his usual active self, scurrying from the computer to the screen, yelling at the top of his voice(thats the way he lectures) , and was saying a lot of stuff, apparently wrapping up. While I tried to capture most of what he said, others just flew past me. There was so much enthusiasm and so little coherence, but Oh well, I have always enjoyed his lectures. I let my eyes and mind wander a bit. The wierd guy was being wierd;chuckling, mumbling perpetually and dressed in a dirty Tee. The guy that sits in the first row was as usual taking his nap, wonder if it was the lecture, the dim lights or its just him. He does not even bother to choose another corner of the room. It was always the first seat in the first row and he's always sleeping with his head thrown back and his legs stretched and apart, not to forget the drooling. The corps guy that sits in front of me was looking at the prof without even blinking, I wonder if this guy really followed Dr.Y 's lectures or if he's just being there, you know like randomly being there. If you took him and put him in "I have no clue 101", he wouldn't even know he was displaced. He'd look just as interested. B was sitting two seats away, relaxed as always with both his legs on the chair in front of him and had his usual calm 'I learnt this in 1st grade' look; One thing I like in schools here is that there are no fake gestures of respect like, sit straight, stand up when the prof enters, don't turn, don't talk, don't drink water, don't laugh, etc., Back in my undergrad, besides doing all this you are supposed to wish them 'Good [time of the day] ' whenever you saw any prof on the corridor. And half the people that acted like they would worship their profs would swear at them the moment they go past them, the other half would act and think the same way. Thats besides the point though, so back to where I deviated.

There were very few people that turned up today; not even K & K that promptly say a "hi" when I come in, were there. Nothing was new, in fact the class seemed duller than usual, why didn't I feel like the usual?. Instead of just being there, I was trying to vibe with and feel the environment. Something about the day and class was different. Suddenly Dr. Y's voice dropped serveral decibels and somehow that caught my attention. Then he slowly and clearly said, " well so thats that, I have said everything I wanted to say. I hope to see you all again, in some other context, in another class, or in the corridor or may be in your work places" . And something hit me.....like a huge bang.."Duh...this was my last class...probably like for ever ". I am confused and I feel like a baby that can't speak or express what it feels. Now am I happy or sad ?...