My first rule of shooting is to shoot the way that brings you the most enjoyment, which you are evidently doing, so I should probably just stop there.
However, never being one to follow my own advice, I won't. If you're not getting good groups when shooting instinctively, then it means you're not shooting using good form. If you shoot using good form with arrows that are well matched for your bow, you should be getting groups somewhere on the target, if not centered on the bullseye, at ranges of 20 yards or less. The only difference changing aiming methods should make is where those groups fall on the target. Focusing too much on a particular aiming method, or on aiming in general, rather than focusing on developing good form will slow down your progress in the long run.