William Black was a great Christian without any singularity or ostentation, ever bemoaning his lack of spirituality and yearning after holiness of heart and life. As he read the lives of great saints of other days, he prostrated himself before God, and craved pre-eminence in the attainment of the higher virtues of religious experience. Humility was one of the dominant factors in his life, which became a habit, through contrasting his actual acquirements in piety, with the saints held in much esteem by the Christian Church. He was extremely sensitive, and this subjected him to periods of mental depression, when he was severely tempted and almost given over to despair. Seasons of melancholy seemed to follow him all through life, especially at the beginning of the year, when he passed under review his life and work. But there were times when he renewed his covenant with God in writing, and when he was privileged to listen to some eminent preacher and mingle with his brethren, that the sky shone with a beauty which was divine, and bliss serene abode in his soul. In one of his seasons of refreshing, when he dedicated himself anew, he writes: "O my God, I am Thine by a thousand ties, necessary, voluntary and sacred. Sanctuaries, woods, fields and other places, have been witnesses of the solemn vows and engagements I am under to Thee, and when I presumptuously violate them, they will bring in their evidence against me. O! by thy powerful grace, preserve me thine, thine forever!" He longed to be like Christ, and yet he could say: "Some appear to be alternately in raptures, and ready to sink in unbelief and despondency: filled with joy, or overwhelmed with sorrow. In general my walk (at least outwardly) has been pretty even. Through the severest exercises I have yet met with, the Lord has not suffered me to be greatly moved. I do not remember that anger ever had a place in my heart for one minute against any one, since I first knew the Lord. If I felt it rise, I looked to the Lord, and was delivered. Blessed be his Name for this! By grace I am saved: and grace shall have the glory. I am never enraptured with joy, nor overpowered with sorrow: yet neither am I without joys and sorrow. At times I feel Jesus inexpressibly precious: and at such seasons I long for holiness, for a full conformity to the divine will."