We believe in something when we doubt it. When there is no doubt, we say we ‘know’. A person that has experienced terrible burns shall never say: ‘I believe fire is hot’. He/she knows perfectly and has no doubt about it. Such certainty is not related to the effort to believe and not doubt.
Human happiness question is not connected to the act for ‘believing deeply and not doubting’. The person that achieves full happiness has no need to believe, as he/she knows clearly and is sure about that.
In the book ‘Why do we live?’, Professor Kentetsu Takamori explains deeply the difference between ‘believing’ and ‘knowing (being sure)’. It is worth reading and having such relevant knowledge for life.
You can buy the book at the bookstores below: