Man sees and knows his own duty, his own righteousness and walking with God; he seeth what it costs and stands him in; he knows what pains he hath taken about it; what waiting, fasting, labouring, praying it hath cost him; how he hath cut himself short of his natural desires, and mortified his flesh in abstinence from sin.
These are the things of a man, wrought in him, performed by him; and the spirit of a man knows them; and they will promise fair to the heart of a man that hath been sincere in them, for any end and purpose that he shall use them. But now, for the righteousness of Christ, —that is without him; he seeth it not, experiences it not; the spirit that is within him knows nothing of it; he hath no acquaintance with it, but merely as it is revealed and proposed in the promises, wherein yet it is nowhere said to him, in particular, that it is his, and was provided for him, but only that it is so, to and for believers.
Now, for a man to cast away that which he hath seen, for that which he hath not seen; to refuse that which promises to give him a fair entertainment and supportment in the presence of God, and which he is sure is his own, and cannot be taken from him, for that which he must venture on upon the word of promise, against ten thousand doubts, and fears, and temptations that it belongs not to him; —this requires humbling of the soul before God; and this the heart of a man is not easily brought unto.
~John Owen
from a sermon entitled Of Walking Humbly With God, volume 9 of Works, page 106-7
The Essential Owen 