How can Christianity be true when you don't actually have to do anything?

This might depend on the particular brand / church but does a Christian in a day actually have to do anything - like you must pray, you must go to Church, you must fast, you must read the Bible?

In anything in life you have to earn it whether it be passing academic exams, losing weight, getting a job promotion... A Christian just goes about his day just doing "what he feels right"? Ex Christians especially please comment.