“It does good to no woman to be flattered [by a man] who does not intend to marry her; and it is madness in all women to let a secret love kindle within them, which, if unreturned and unknown, must devour the life that feeds it; and, if discovered and responded to, must lead, ignis-fatuus-like, into miry wilds whence there is no extrication.” ― Charlotte Brontë
“[It] was the first time in my life I ever knew the meaning of that rare thing, tenderness. A quality different from kindliness, affectionateness, or benevolence; a quality which can exist only in strong, deep, and undemonstrative natures, and therefore in its perfection is oftenest found in men.” —Dinah Maria Mulock Craik
“The reason for the unreason with which you treat my reason, so weakens my reason that with reason I complain of your beauty.” Cervantes from Don Quixote
Or, maybe better...
"The heart has its reasons of which reasons know nothing." Pascal
“Perhaps all the dragons in our lives are princesses who are only waiting to see us act, just once, with beauty and courage. Perhaps everything that frightens us is, in its deepest essence, something helpless that wants our love.” ―Rainer Maria Rilke