I think that it's very different for everyone and sometimes a little can find fun in unexpected places!
I'm trained as a graphic designer but because the field is so competitive everyone who wants a graphic designer usually goes for someone with way more experience. I worked in retail jobs for a long time and that was bad, bad, bad for me. Maybe some littles could find a way to have more fun with it but not my shy, quiet self. There were some aspects of it I could have fun with, like sometimes I got to talk to kids! And I connect with kids very well as a little.
Now I'm doing custodial work. Maybe you are thinking "oh, cleaning sounds yucky" but for me it's fun! I have to be responsible and clean lots of stuff but I'm all by myself late at night while I'm cleaning. I can listen to any kind of music I want, I can skip down the halls or dance, I can play finding games sometimes too and find treasures. Like sometimes people at my job are throwing away cool things and it's ok for me to take it for myself instead! I also like to bring my toys along on some days and I have my lunch break and I talk with my toys. Sometimes people come by but I'm all alone during most of my shift so I can have fun while I work without worrying about being embarrassed. Also the place I'm at pays pretty well and gives me lots of paid holidays too! I'm surprised by how nice this job is!
Sometimes you can find a job that is better then you expected. Even if it's not your planned dream job (mine was art-related and so far it hasn't worked) sometimes you can be happy in a different place!
I also think there's a lot of ways a person can be little at work too, to give them a happy boost. Even when I was working in retail and having a bad time bringing myself some candies to eat while I was working helped a lot. You could put some good stickers on your stuff like maybe a lunch box and give yourself boosts during a tough work day. You can try to be imaginative for a few minutes and find ways to play subtle games no one notices. I think really a little can find a way to be little or to have fun in many different kinds of jobs. Just be creative!
When it comes to college specifically I just think you got to think about the things you like and try to learn stuff that is cool to you. I liked art so I went for art. If you like science then go for science! College is so cool, because in my experience the classes there are so much better then in other school classes. In college you get to learn the stuff YOU think is interesting! Every little is a different individual. Some littles love math and think math is very fun! Some littles like to be big thinker philosophers! Some kids think history is real, real neat!
Always have good luck with whatever you do and just try to have fun!