Iphone 5s Lagging along with some games.

i am using Iphone 5s and have update my phone to latest IOS 7. Some of the games that i have installed are lagging on my Iphone 5s. i have read some blogs they say that its because of Contrast On. And i have tried this and it is true. But my phone is lagging too...Kindly help me out... Tell me tips so that i can keep my Iphone 5s fast and smooth and games too...along with my Contrast Off...