All you need is focus. At 14, that can be a difficult thing (if I remember correctly… my memory isn’t what it used to be 
As Jezcentral suggested, break things up into
smaller
pieces.
Game development is probably the most multi-disciplinary field of work out there, so it’s very easy to get into a state of cognitive overload and/or sheer panic from time to time. I’d say the key skill you should develop at this point is The Power Of Tunnel Vision… i.e. the ability to focus all your attention on one tiny aspect of an idea or skill, while ignoring everything else that is peripheral to that, for some extended period of time.
switch to another tiny thing.
Repeat.
After a few years of that, you’ll be more comfortable and confident about it.