My thanks to Peter Turner for recommending the book Orthodoxy (Dodd, Mead & Co., 1908) to me some time ago, and therefore making this answer possible. Thanks to Kindle full-text search, I found the following in Orthodoxy chapter 5, The Flag of the World:
Love is not blind; that is the last thing it is. Love is bound; and the more it is bound the less it is blind.
This at least had come to be my position about all that was called optimism, pessimism, and improvement. Before any cosmic act of reform we must have a cosmic oath of allegiance. A man must be interested in life, then he could be disinterested in his views of it. "My son give me thy heart;" the heart must be fixed on the right thing: the moment we have a fixed heart we have a free hand.
[My emphasis. The quotation "My son give me thy heart" is from Proverbs 23:26. "Thy" is the choice of the Douay-Rheims version, where the KJV has "thine".]
The overall context of the chapter is Chesterton's rejection of the philosophical abstractions of optimism and pessimism: neither of these is sufficiently rooted in the real world. He argues that we must feel an allegiance to the world in order to be champions for its improvement. The optimist, he says, is likely to declare that it is in no need of improvement; the pessimist, that improvement is not possible: "Can [the ordinary man] hate it enough to change it, and yet love it enough to think it worth changing?" The comparison with romantic love is that we do not love abstractly - we love particular people for who they are. Regardless of good or bad points about the world, we are invited to see the world as worthy of our interest, and worthy in itself rather than as an exemplar of goodness or badness.
In general, Chesterton finds ideals which are disconnected from real experience to be insincere and futile. This is placed in contrast with the Christian faith, founded on a specific individual who said and did surprising things. He found that while he could not build his life around - for example - the abstract notion of Goodness, he could do so for the specific person of Christ. It is not only a matter of psychological "fit", but a practical one, since Christ does a better job than Abstract Goodness at supplying actual moral guidance. Further, Abstract Goodness cannot love or be loved: Christ can.