I have a high metabolism, must I eat perfectly?

Considering your age and what you've said of your body type it all comes down to your fitness goals. If you want to build lean body mass and toned muscles you will have to eat much more than you are used to. This doesn't mean milk hakes and burgers but a balanced diet built around your metabolism. With out getting too technical the hormones in your bloodstream will tell your body what nutrients to use and how fast to use them, so in your case of the nutrient being used up faster, you have to beat that out by eating more. I would recommend a rough outline of 30% Protein, 50% Carbohydrates and 20% Fats for your needs if you want to gain strength and definition. Be aware that metabolism begins dropping for women after age 20 or so. Hope that helps!