Saint John of the Cross

It is a matter of real sorrow when God has given those strength to break stronger fetters, those of vanity and sin, that they neglect their own progress and the attainment of such great blessings because they will not detach themselves from trifles. Not only do they not advance, they fall back. For it is well known that on the spiritual road not to go on overcoming self is to go backwards, and not to increase our gain is to lose.As wood can never be transformed into fire if one necessary degree of heat is missing, so the soul that has even one imperfection can never be perfectly transformed in God.

-- Saint John of the Cross