Not long ago I was preaching at a local church and the Sunday school class I sat in on (ages 18-30 or so) was discussing spiritual discernment and maturity. The definition I gave to them for spiritual maturity was as follows:
Spiritual maturity should be the ever increasing state of a believer's spiritual life when he ceases to constantly attempt to justify what he wants to do by pointing to the things that aren't clearly spelled out in God's word, and he begins to seek only to glorify God through simple obedience to the commands that are clearly spelled out in His word.
Once the maturing believer is being guided by the Spirit of God in obedience to the Creator and not being constantly controlled by any other motivation, he begins to realize just how useless this world's wisdom and pleasures are when it comes to fulfilling the will of God. Neither Godly wisdom nor Spiritual discernment are required in order to accommodate one's own fleshly desires and it would seem to at least be close to blasphemy to attribute the pursuit of one's own desires through devilish wisdom to the discernment of scriptures by the power of the Holy Spirit.
That is why true discernment begins to manifest itself in large part when one realizes that the pleasures of this world, be they overt sin or "merely" omissions or just whimsical participations in the popular, are mutually exclusive from doing the will of the Father. It is simply not possible to serve two masters.