I think it would help if you were to do a project in which you're not taking the lead. A project with a leader.
From what it sounds like, you're setting your own goals and projects, then being disappointing when you don't have the motivation to complete it. If you were to take part in more projects where other people tell you what to do, where you have clear goals given to you and you KNOW what you have to achieve, where you can see the end result you will be getting from the project, then you may have some solid work to your name and will not have the motivation issues you are having because you will be more dependent on other people. Particularly at your age, you will learn a lot more this way and be much more efficient.
So for now, leave it to someone else to worry about all the details you mentioned, and just enjoy being in a game dev' team instead of dumping all the pressure on yourself