Adjusting to full time college life is hard when you're a freshman (or so I remember). "They" say it can be hard on anyone, and everyone has some adjustment issues at some point. I'll buy that, having been a freshman once.
"They" also say, and so do I, that going back to college as an adult is hard, too. You're in a different age group, with different perspectives and attitude. If you're at a college with a decent number of other older adults, it's not so bad-- you can usually find someone who remembers Blue Oyster Cult never being about "more cowbell". (At the community college I attended, there was always at least one other older adult in all of my classes.)
Going back to college as an older adult-- real college, full time college, I list "student" as my occupation on my 1040A, I'm not just "taking classes at night"-- is a different thing entirely. It's the dream, it's what I want to do, it's where I want to be, but damn it's hard to get the logistics right. It takes a lot of thought and effort to get everywhere I need to be, work on everything I need to work on, and still do normal people things. You know, things like grocery shopping, laundry, exercise, and social life. I should be studying right now, but I have to do laundry, and do dishes, and straighten up the apartment, and get my disability paperwork finished, and...
It's not so much that I'm slacking, although I hear the voices in my head telling me that I am. It's that the process, the logistics, the daily grind of being a student who lives off the campus grid is exhausting. I spend so much time and effort just being a student that I don't have enough energy left to be a student. The PTSD makes it harder, because to get all those things done I have to wade through triggers, deal with intrusive thoughts, get past stuck points, settle myself down, and constantly get myself back on track.
I am working on changing things-- I'm moving to a new apartment a block from campus in August, which will eliminate two 40-minute bus rides a day. I'll be able to go home during the day, to do things like eat and throw in a load of laundry. I'll be across the street from my favorite library. I also won't have to carry around 30 pounds of books, supplies and laptop all day.
Next semester, there will also be 4,000 people on campus who are more lost than me, and I won't have to give the "well, it's my first semester here, I transferred from... blah blah blah" speech quite as often. I hope.
Until then, it's just hard.