Born working class/single-parent family at a time when university education was free. Cannot emphasise enough how this affects parental mindset as well as kids'.
Constantly encouraged to go further than home town (travel/books/talk). Yes to being lucky as in no disability/illness/caring duties.
Was bright at school, am now distinctly average but love learning new things so teach myself all skills I need (even if I then outsource).
Learning online is often free, or at least cheap when you factor in how much it costs and the time you spend communicating what you want to other people. I always make an investment in tools to make the job quicker and better.
I'm not super confident, I haven't read any 'clinch those business deals in three minutes' books, but there's a pattern to interactions. People want to see that you know stuff about your sector and people within it, that you ask the right questions, that you aren't an arse, that you have a plan and therefore aren't a flake. You'd be surprised how many people are absolute flakes and things fall into their laps but they have zero idea of how to progress. (It's not good to underestimate people in general but that's my confidence-boosting tip there!)
Do the work, learn the stuff, make relationships with people, put the hours in where you need to so accept that 11pm emails are sometimes necessary. But above all just do stuff. Exercise is great, sleeping well is great, but I'm quite fat and wake up often in the middle of the night - it doesn't matter because the work is getting shit done, and preferably not paying other people to do it ;) at least in the beginning.
Oh and don't fuck about on social media or within your sector getting involved in arguments (it will be checked if anyone is thinking of working with you, and it is easy to find people behind pseudonyms - I do this regularly and have definitely not taken jobs forward with people who are clearly a PR liability and/or UKIP supporters, even if their work is decent).
I suppose what I am saying is that you don't need to be hugely over-confident, just not socially anxious...you don't necessarily need to be in tip-top physical shape...you don't need to be super bright. You do need to be the person who can go 'I can do that' or 'I can learn that' and then - and this is crucial - you need to actually do it, on time and within budget.
And lastly, you need a bullshit alarm, because people absolutely will exploit you if you have a grab bag of skills - even nice people with high profiles. If they can pick your brains as a shortcut, they will, and you end up with nothing. It's not necessarily calculated on their part, it is just the norm. So turning their ideas into genuine opportunities for you is also a skill worth developing, and quite often those same people will respect that you have a plan.
Get to it ;)