A disciple of Jesus Christ offers his life unto the Lord and others as a living and holy sacrifice. Such "dying to Self" (Matt 16:24, 1 Cor 15:31, Phil 1:21) is acceptable/pleasing to God. And given what Jesus Christ did for us, it is our reasonable/rational/logical service to Him (Rom 12:1).
We prove/discern this will of God by not conforming to the world, but by being separate unto Him and separate from the world (2 Cor 6:17-18), and by being transformed by the renewing/renovation of our mind/intellect/thought process (Rom 12:2).
The transformation of our thinking is a. From darkness to light (Acts 26:18) b. From righteousness by works to righteousness by grace (Eph 2:8-9) c. From justified by the Law of God to justified by the faith of God (Rom 3-4)