Oh Spiros you sound like me two years ago. Even the writing thing, speech, confidence thing...me to a tee! If you look at my first post on here, I wrote something like, "I'm not very good at writing".
But there is hope my friend!
I figured out it was all utter crap! But I think I understand why I did it to myself...basically it was my inner self, trying to stop me from doing things that weren't the real me. I was not ballsy enough at the time to really look deep within myself and be selfish enough to ask myself what I really wanted to do in life. If I had looked deep within, I would of realised that I just hated working for other people, that I liked creative freedom and I would be stupid to waste all my talents on making money for other people. So my inner self kind of took control and did things to self sabotage me. I didn't understand at the time why I kept on putting myself down. I just thought I was worthless and I had a curse of some sort. But now I look back and it was basically a way for me to manipulate my mind. This is where I have come to realise that there is more going on with our mind than we realise. Our "inner something" takes over when we can't verberlise out loud what we want.
So for example I would tell myself I was the worst writer in the world and so I could never get a job, which required any writing. Unfortunately, all the jobs in my field require good writing skills to write up proposals, but because "I was not good at writing" it canceled out most jobs for me. But then of course there were the jobs that required speaking as well, now I could barely pick up a phone, let alone speak to people about ideas, so that crossed out quite a few other jobs in my field.Then there was the problem with me talking to people in high up authority, I would crumble at the knees when someone powerful was in front of me. But then I thought I have to do something what about a working a cafe...nope can't add and subtract quickly enough (yep I did the same thing as you). It's true I can't add and subtract quickly, and never learnt any of my times tables. But there's a reason I don't have those skills...they just never interested me
I'm the type of person, that if it just doesn't interest me I just wont bother with it no matter what. I'm fine with being not good at maths...don't really need those skills anyway for what I do.
So basically I came to the conclusion that I just wouldn't be able to work for anyone because they would soon realise I was an absolute loser with no skills at all.
But the fact is that's not that case I have many skills, and good ones at that. Too many good skills that would be wasted working for others. I would only able to utelise a fraction on my skills and enjoyment in working for others.
I'm not sure if a lot of how you feel, is because of your work situation...for me it was. So that's why I am talking about it from a workplace perspective.
I will leave you with two questions my friend, Spiros do you hate authority and have you ever had an entrepreneurial mindset?
If you do have an entrepreneurial mindset, your post suggest you might as you say you jump from one thing to another and lose interest with things quite quickly. It could be stress or it could be because your entrepreneurial. If you do have entrepreneurial tendencies then read this book
Amazon.com: Refuse to Choose!: A Revolutionary Program for Doing Everything That You Love (9781594863035): Barbara Sher: Books I'm happy to post you my copy if it helps.
Oh and I am a fellow Aussie too