I cant get the hang of my tennis racquet?

Ok I recently purchased a HEAD YOUTEK EXTREME (MP) TENNIS RACQUET. It is has an 100 inch head and it weighs 11ounces strung. I started playing tennis a couple of months ago. I used other racquets that were heavier. I found that they are alot easier to use because I would get easy acess to power on my shots. Also there is times were the react late and I don't get the full rotation. So once I got this racquet I knew that it involved faster hits because it was light but I just cant get used to it. My serves and flat shots are weaker because it is so light. My friend said it takes getting used to and that i need to always do full swings. I tried out his bablomat aeropro racquet and I found it much easier to use. I had better serves and my flat shots were incredible. I really dont want to have to buy another racquet. What should I do to improve my game and adapt to this racquet or is my only choice getting another racquet?