Good question, especially the part: “how to make good decisions every time.”
This is the basis or the foundation of the Noble Path.
As we know, before giving up the householder life, the Buddha was a prince and had a son, Rahula. Rahula also became a bhikkhu at age seven. Buddha’s advice to that young Ven. Rahula is detailed in the “Ambalaṭṭhikarāhulovāda Sutta (MN 61).”
A fairly good English translation is, “Discourse on an Exhortation to Rāhula at Ambalaṭṭhikā.”
The first part of the translation is not very good. But starting with the section “Reflection before Action” the translation is good.
– Please read that sutta and ask questions if clarification is needed.
Basically, the Buddha was telling Ven. Rahula that he should always be mindful of his actions, speech, and thoughts.
– If any of those can bring harm to oneself OR TO others one should not engage in such actions, speech, or thoughts.
– These are dasa akusala.
Furthermore, one should actively engage in actions, speech, or thoughts that would be for the benefit of oneself AND to others.
– These are dasa kusala.
This is discussed at, “Ten Immoral Actions (Dasa Akusala)”
P.S. Since you mentioned Kāyānupassanā, it is discussed at:
“Mahā Satipaṭṭhāna Sutta“