Uhm, sorry for my bad English. Please bear with it :)
I think the problem most teens face is their lack of resources. Lack of information of their desired career, lack of experience, lack of financial support and sometimes lack of encouragement of those around them.
Some teens (such as myself) usually pick a career because it sounds awesome or cool. Sometimes they don't weigh the pros and cons of their chosen career. Because of this, some teens get into career that don't suit them.
Most jobs nowadays ask for an unreasonable range of experience. This is something teens lack. They can only usually apply for small jobs. Unless they chose something like making music or being an actor/actress, they would have a possibility of being happy with their career. But some of them don't have the time to pick up an instrument or take acting classes. Some don't even have the talent or desire to do these things.
Now if they chose to go to college to get into a career that is their kind of field then it might just be destiny's way of paving the road for them. But other teens aren't so lucky. There are teens that don't have a single cent to their name. This of course, is a big obstacle most can't overcome with the time they have. Sure, getting a scholarship is one way, but in some scholarships, you have to pay off the money you obtained. What assurance do we have that we get the job we desire. Again with the experience. Most jobs ask for a lot of experience in the field, but if all of them ask that, where will they go to work?
Some teens just lack the encouragement from the people close to them. This can be a big problem because most teens are all about acceptance from those people. I've hear that in India, most parents tell their kids to become an engineer or a doctor. Culture, I guess. Parents usually tell their kids they know what's good for them. But what if the career isn't really meant for them? This leads to teens losing their way to their proper career. A career for life, if you must.
I hope it's not too long. Hahaha. These are just some of the things most of us face.