Why does beliving in god mean you have to dedicate ur life to him?

i dont belive in god because my parents made me go to sunday school and m every sunday for my whole life and all the things they say in m sound obscure to me such as god likes it when you suffer ...god wants u to suffer for others .....your entire life should be about god ..fill yourself with god...dedicate yourself to god..dont have ...dont do any ting pretty much that makes you happy ..dont do anything unless its about god... can someone explain the reasoning behind this because frankly i think its ridiculous ..shouldnt life be about making yourself happy making yourself a life of your own and depending on your strength to make it through life why is it so bd to make yourself happy by having ..or lusting ..or indulging..