Having a fast metabolism means you'll lose weight fast... or at least faster than if you didn't have a fast metabolism. Do you want to speed up your metabolism? If yes, that is a good thing. A fast running metabolism burns off calories even when you are at rest. That is you'll lose weight while sleeping, lose weight while driving the car, drop calories while watching the TV. It's like an automatic diet.
It comes with work and nothing is easy. The article I have linked will show you how to speed up your metabolism.

Learn how to judge the amount of food you need, and what is a healthy level of calorie cutting to diet, maintain weight, or fuel a heavy workout schedule. Find out how to tell the signs of starvation and combat plateaus.

How many calories (kilojoules) in one day?