... or do you think that perhaps a depressed mood might be a factor here? ... and the latter can be helped medically.
Willpower can defeat any mental problem. Generally, people (myself included) will accept having a mental illness because it excuses certain behaviours. I've come to terms with the fact that I could absolutely have depression. Though, given my circumstances, I could just as easily say that I am a victim of oppression. (I'll explain in PM if you want me to)
If you decide to accept a mental illness, then it
explains why you exhibit certain traits. For me, I only exhibit the traits of depression some of the time - and it heavily depends on what's going on. I don't like the idea that I might have a mental illness but, deep down, I know that my brain has accepted it because it is now a chore to get out of bed in the morning.
To be honest, all you have to do is believe the opposite of what the mental illness might make you think - which seems difficult, but you don't need meds for it.
Back on topic - Negative thinking will yield negative results. If you choose to believe that you're not good enough for a job or that you'll hate tertiary education (which isn't entirely essential these days), then you will find it much harder to find something. I know this from experience. I'm currently unemployed and a university dropout. It's becoming harder and harder to come up with the motivation to find work. You
don't want to be in my position. Trust me.
Look at something and see it for the good things it can get you - experience and money are two of the more important things. You can also make friends, which is really good. You might even find your personality changing for the better, you'll likely be happier and more confident.
Change the way you look at jobs and education, not for what problems might occur (because that will effectively mean you do nothing in life), but for the opportunities it presents.
That's what I'm trying to do.