Lol obviously you are much more experienced than i am and it sounds so much better better in theory than when practised.
I obviously did start out playing demo accounts, blew a couple of those till i got the hang of it. After i tripled my account in about 8 months i dont think i cant take it seriously anymore. There is no risk involved and like you pointed no emotions. In demo you can take any trade and be carefree where as in live you have emotions attached to it.
I believe i am pretty good when it comes to risk managment. Now and on my demo...
But if you are still blowing accounts then if that was me I would still be trading demo. Or at the very least only be trading be capital that I am comfortable losing while you are learning. You have many years in front of you and the markets are not going anywyere. Most at the age of 17 would not even be thinking about the markets.
Trading most certainly is not easy. But can be very rewarding.