This is the mother of all logics.
Azt csinálom, amit akarok és akkor, amikor akarom. – mondta a beképzelt milliomos.
I do (definitely) what I want (indefinitely) and at the time when I want (definitely) it. – said (definitely) the cocky millionaire.
If you understand the reason why, good for you. I just find it easier to keep my eyes and ears open in what I am memorizing to find where things start getting consistent. Every time we use “mit” we use an indefinite conjugation. Every time we use “azt” we use a definite conjugation. Every time we use “amikor” … uh… uh… let’s not be misled… perhaps there is an implied “azt” there: Amikor azt akarom.