The answer may seem to resemble Gnosticism. But only if you accept a ‘one sided’ understanding of that term ‘Gnostic’. So before answering the Q, let me explain this
Gnosticism has been used to describe (or usually defend) anything to do with ‘Christianity’, as soon as you mention ‘spirit’. The gnostic belief that ‘physical’ is bad, and ‘spirit’ is good has ‘some truth’. N.B. Some, that is, an element.
Where the Gnostic”s go wrong with this is in the origin of the ‘good’ [spirit] and ‘bad’. [physical].
Adam and Eve having their ‘eyes opened’ after eating - was according to Gnosticism, good. That ‘enlightenment’ after eating is what they ‘link’ to ‘secret understanding’.
As for flesh, flesh is everything apart from the spirit. So, your ‘soul’ and your physical senses (body). When a believer is ‘reborn’, their ‘spirit’ is made alive (renewed). And now that needs to be the source for wisdom. That is ‘live in the spirit’. And the spirit gets its wisdom from the word. So your mind gets renewed by ‘listening’ to your spirit [the word] instead of your natural reasoning [learnt via your ‘senses’.].
GAL 5:16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
Prior to being ‘reborn’, you can/could only ‘live’ in your flesh - because your spirit is ‘dead’ - that is - separated from God, courtesy of Adam.
Some Believers can become a little cautious when talking about the ‘spiritual’ dimension - (sometimes rightly so.)