Thy kingdom come, thy will be done, in earth as it is in Heaven. (Matthew 6:10, King James Bible)
And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation: Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you. (Luke 17:21-22, King James Bible)
What is the ‘Kingdom’? In contemporary terms, it is a grass-roots, metapolitical movement, which comes out of the theosis (spiritual development) of individuals and then the actions they take.
Norman Vincent Peale’s The Power of Positive Thinking (1952) is largely a collection of practical tricks for changing how one thinks on an habitual basis and therefore acts (i.e., theosis).
These practical tricks are part-and-parcel of kinds of Christianity, and Peale (a pastor) explicitly couches them in the Christian Gospel. The Gospel isn’t incidental to many of the practices – rather, the practices are closely connected to parts of the Bible, and probably generated in part by reflection on those texts (so, the texts acted as a kind of heuristic).
In light of work by Nassim Taleb on antifragility, the following one in particular I found interesting
6. Avoid argument, but whenever a negative attitude is expressed, counter with a positive and optimistic opinion. (p. 172)
The trick here is to create an ‘antifragile’ process (something that gets stronger when exposed to intermittent stresses, such as a muscle gets stronger when lifting weights, say). A negative attitude, which ordinarily might damage a positive attitude, is used as a stimulus to create a stronger habit of focusing on positive or optimistic ways of thinking. A nice trick.
Many antifragile processes are part of Christian practice, just as they are with certain kinds of Stoic thought and practice. For example, detachment from material wealth means low downside to lack of material wealth, but upside to having material wealth (as with Seneca).