If we regard Goodness as living in harmony with God's creation and creative purposes: then we are able to do this because there is divinity within each of us. In other words: we are God's sons and daughters; which I understand to mean that there is a literal (procreative, not symbolic) sense in which we have been made divine, in our souls.
We are not fully divine (as was Jesus Christ) but we each have that potential - and to have that potential we must be (and are) partly divine.
It is this aspect of "God-within" that enables us to want Good, and also enables us each to discern and know The Good.
OK. So we are each a God-containing, partly-divine being - living our mortal lives in this world.
As such; and we need to learn from our experiences in mortal life, lessons that which will be of value in resurrected eternal life (i.e. theosis); and we also need to desire and make choices such as to reach that resurrected eternal life after our biological deaths (i.e. salvation).
How are we enabled to discover guidance in navigating through this complex world? Especially considering that we are each unique and changing, and live in unique and changing circumstances.
Because our guidance needs to cope with unique and changing personal and life problems - then it seems clear that generic and fixed answers will be insufficient.
Salvation and theosis must therefore be 'bespoke' - that is, 'made to measure' for each particular human soul; because 'off-the-peg' guidance (such as that provided by generic church teaching, practices, supervision etc.) cannot take into account our unique circumstances and nature. This generic guidance is always inadequate (even though it may be helpful).
Our personal guidance is available from both directions: from outside us, and from inside.
From outside; God is the primary creator; and continues His work of creation - and (because we are God's children) this creating extends right down to the level of each of our lives.
Therefore, we are guided by God by means of his creative work in arranging of the circumstances of our each of lives.
This guidance may take many and various forms, starting with our nature, abilities, circumstances of birth and parents; and including what might be termed 'luck' and 'coincidence' or 'synchronicity'.
This guidance from God ensures that we are given the necessary opportunities and choices by which we can (from our our agency and by 'free will') attain salvation, and learn valuable lessons from mortal life.
External guidance from God is therefore from the direction of outside - by creation acting upon our lives. This is met by the guidance of the Holy Ghost which is experienced from 'inside' us.
Led by the Fourth Gospel (called John); I regard the Holy Ghost as our (potential) relationship with the ascended Jesus Christ. Such guidance is accessible by those who (whether explicitly, or implicitly) desire Heaven and have chosen to follow Jesus Christ - i.e. be guided by Jesus Christ.
The guidance of the Holy Ghost is therefore an inner personal relationship (which is why the Fourth Gospel uses the synonym of 'comforter') that will inform us of... whatever we need to know for salvation and theosis.
Again, it is a matter of our chosen free agency whether we follow this guidance.
In sum: we can envisage the scheme of guidance as coming from from outside us - as God creatively-shapes the circumstances of our specific mortal life; and also from the opposite direction: from inside us - as Jesus personally-guides-us through the unique circumstances of our unique lives.