Existentialism generally is a philosophy associated with atheism. The majority of existentialists are atheists because the basic tenets of their belief do not comport with a God who is omnipotent, omnipresent, omniscient, and in charge of everything.
How can a stellar existentialist, who is steadfast in his independence, tolerate a controlling God? How can an existentialist believe that he is making choices if everything is predestined by God? How can a good existentialist believe that life is absurd and without meaning if there is a God?
Well, these are excellent questions, but there are logical answers for Christian existentialists like Soren Kierkegaard: (1) God gives us free choice and does not interfere with our decisions; (2) God created our universe outside our universe, since matter and energy can neither be created nor destroyed in our closed universe; in other words, God created, but does not control our universe; (3) nothing is predetermined in our lives since we make choices and suffer the consequences; (4) and life is absurd without God.
So, it is possible to be a Christian existentialist. You will not have many friends or associates who agree with you, but you can always unite and communicate with the most important entity, God. Becoming one with God should be your primary goal in life.
The first step in being a true Christian existentialist is to reject other Christians who are not authentic. Unfortunately, this is a high percentage of modern Christians. Most Christians go to church for social approval and cannot discuss theology or even basic concepts supporting what they really believe. In fact, most of them don’t believe in anything other than making appearances and looking good in the community. Their beliefs and faith in God are only skin deep.
How do you become an authentic Christian existentialist? Well, it will be a bit controversial, but you need to reject family, peer, and social pressures to think and act a certain way. Then you can start meditating or focusing on what you really believe. Let God into your heart and make Him a part of this process. Become one with God. Seek harmony with your freedom to make choices and be prepared to accept the consequences from poor decisions. If God is within you, you will find peace in this process.
God will remove the anxiety and existential angst in your decision making because He will lead you. Even though you cannot see God and even though He is not inside our visible universe, He can enter your soul as the Holy Spirit and become unified with you. Your conscience and awareness is heightened with Him inside you. Your choices may not be perfect, but your attempts to improve your decisions with humility will be all that matters if you fully accept responsibility as one who is imperfect.
And remember: life truly is absurd and makes no sense without God.