The central difference between a believer and an unbeliever

The grand central difference, from whence arise all the others, may be thus express
He before thought, that there was a necessity for him to find some saving change or good disposition wrought in him, before he could have any peace in his conscience, or rest to his soul, from the perfect work of Christ presented in the gospel, and accordingly was distrest in his thoughts for want of perceiving it in himself, and therefore sought after it, and prayed for it, that he might obtain peace and hope towards God. And when he apprehended that he had found or obtained it, he laid the chief stress of his hope upon it. But now he finds relief to his conscience, not by discerning any favourable symptom about himself, but by understanding that blood of Christ is all sufficient and free, according to the divine testimony and this evangelical peace and rest thus obtained, becomes the root and spring of all that love and obedience, which distinguishes a believer from others. And so he now rejoices in Christ alone, having no confidence in the flesh. Phil 3.3. -Samuel Pike, Free Grace Indeed!, pg. 79