What makes people cheerful? God makes them cheerful at the cheerful times. When they doubt God, then they become cheerless. If they trust God, they can be cheerful in many troubles. God makes them cheerful.

People are cheerful comfortable conditions of life and lack of health problems, and not faith in God. Many atheists are much happier than religious people. It seems to me that sometimes religious people are unable to enjoy life because of the stupid prohibitions of their religion.
As a christian i will say that nothing prohibits us from enjoying life as we see fit, The Bible says itself that we are free to do anything that we like but it also states that not everything that we do is beneficial for us. You can drink and smoke but its not going to be good for your health in the long term.