What about the miserable guy at work?

How do I continue to be a forgiving and loving person to someone that is miserable? I see them as a joyful/playful/hopeful 4 year old. And I interact with their childhood spirit rather than their current negative persona (a pile of layers that they have built up over time). This makes it much easier to treat them with love/kindness, knowing that deeply buried inside them is a joyful and loving 4 year old.