Religion is accepting speculation as truth, that creates the fake sensation of control over things that are impossible to control like death for example.
All traditional religion are cults of death and resurrection, where the main prophet ultimately overcomes his human nature by facing death and coming back or live forever in haven.
People that follow traditional religions do so because by worshiping God they expect to gain magical power that defy the laws of nature that we are all ultimately bound to. If you really believe in God and you pray you can expect miracles, not to mention that they believe that to some degree they re immortal, because the soul outlives the body and joins God in Haven.
This tradition allows them to deny their own mortality and soothe the anxiety that always exist, because we are aware of the fact that we are going to dye one day.
If you are not a religious person, you might be an atheist or a man of science etc., this are religions within themselves because they are still based on speculation design to sooth ones anxiety by giving him a false sense of control over things that are impossible to control. It is impossible to know everything, you can only have seeds of truth, you ultimately have to fill the holes with speculation which means that you have to have faith that your speculation is truth.
If in a traditional religion the syntheses is put on having faith in God, in all the other religion that doesn't call themselves a religion the faith is place on the impossible to fully prove hypotheses.
Because ultimately our anxiety is based on the fact that we are eventually going to feel pain, fail, be a victim of violence and eventually dye. In order to remain functional you have to somehow suppress it other wise you would just be in a state of grief all day and wouldn't be able to accomplish anything. You could say that you can be only in two states in life, suppression or grief.
From this need of suppressing our anxiety, we have to always speculate and place our faith in the fact that what we speculate is truth, to remain functional. Even if you reject all traditional religion or science, you will basically end up with your own unique philosophy which it is impossible to fully be proven so you are basically creating your own religion.
The old idea introduced by Sigmund Freud that suppression causes mental illness, is like saying that sugar consumption causes diabetes. If that would be true why doesn't everybody that eats some candy develops diabetes, there must be other factors that determines the cause of the disease.
Suppression means you have a healthy mind that keeps you functional, by not allowing you to constantly think of all the horrible things that could happen to you at any moment. It is the complete rejection of these facts that will make them linger even to the point that will make you dysfunctional. For example if you want to never fail, you wont take any risks which means that you will hardly learn anything so ultimately you end up being incompetent because you don't accumulate any skills, which is going to increase the amount of failure in your life.