Donald Farfrae is a man small in stature yet large on principles and self-control. He acts according to high moral and ethical principles in all things, so that when he is impelled into competitions against Henchard, he never feels a personal vindictiveness or mean-spiritedness. On the contrary, Farfrae feels a genuine compassion and respect for Henchard. This is clearly shown after Henchard's bankruptcy when he asks Farfrae for a job. Farfrae gives him one and is careful to arrange things so that he never personally gives Henchard an order.
Farfrae is friendly, personable and well liked. Yet he maintains some reserve that allows him to calmly think things through and choose courses of action that lead to good and sound future results. Thus his path through life is smooth and productive (compare this to Henchard). In conjunction with these qualities, Farfrae is also methodical and careful in what he undertakes. This furthers his success so he has ever expanding control over his fate through ever expanding choices available to him.
Some might think him mercenary for abandoning Elizabeth-Jane to marry wealthy Miss Templeman, but his reserve allows him freedom from ill-founded emotion and his methodical carefulness allows him wisdom to see that a marriage between himself and Elizabeth-Jane would be unwise and encumber both of them because neither one had the financial resources to build a good life upon. This points out the most important quality in Farfrae's character, that of being able to look to the future to see the ultimate outcomes and consequences of his choices in the present day. This resonates with Hardy's twin themes of Fate and the interaction between choice and Fate, and it is in direct contrast to Henchard's impulsive plunging forward without thought to future effects.