Hey kid, I hear that you are 12. You have 6 years left of mandatory full time education [UK]. What you need most of all is balance.
Yes, you must do some subjects that aren't your favourite but try hard and you will get the opportunities that are suitable for you later. Don't forget to play but remember to both work and play. Choose subjects that you are good at, enjoy and that will provide you value in your life ahead. You get to decide what "value" means.
The other key point is to understand the difference between goals and aims. Goals are targets you will attempt to achieve whilst aims are where you are currently heading. So you will succeed and fail many goals (mainly succeed, right!) on your way to ever changing aims (or you might be in the tiny minority where they may never change). It is OK to never get to a particular aim and yet other aims may become goals.
You are 12. I get that. Focus on what your goals are (exams? scouts? learning to bake at home?) as you will have many and only consider your aims (Nurse? Musician? DBA?) when you have to decide something (even if only to tell Aunt Agnes what you want to do for a living when you are older) but always bear in mind that for most of us our aims change.
Good luck. Most people will be rooting for you.
-- Stop your grinnin' and drop your linen...they're everywhere!!!