Let me expand on this idea a little, so you don't get the wrong idea. First year is a lot like the first book/movie in the Lord of the Rings trilogy: The Fellowship of the Ring. Everybody is nice and optimistic about things, they all feel like they have a purpose, and everyone is working together as a team to some degree to help each other accomplish that purpose.
However, the end of spring semester is alot like the end of Fellowship and the beginning of The Two Towers. The motley gang is disbanded by forces beyond their control (the summer) and everyone is left to either fend for themselves or survive off the land in splintered factions. Come next fall, folks stop going to lecture, and even when not in lecture there just isn't as much time away from studying as one would like. You may maintain friendships or even make new ones, but you won't have a ton of time for socializing and there just isn't that uniting force that there was in the beginning of M1 year to bind you all together. You end up feeling a lot more like a free agent than a member of a team striving for a shared goal. Doesn't necessarily mean that we try to gun each other down, but I (at least) find myself a lot more absorbed in what I need to do to get myself through this mess, rather than how others around me are doing (with a few exceptions 😉 ).
Then again, maybe it's just me, and I'm mentally preparing myself for next year when they really split us all up.