It would be very useful if words like meu / minha were described as being masculine / feminine, when introduced in the training. It often takes me some time to realize that's why they're being used differently.
I understand. Just try to remember that most feminine words end with 'a' , while most masculine ones end with 'o'. Of course that doesn't apply for meu, but the rule still works if you think of it's opposite, which is minha.