Why has Gilbert’s mood changed towards Helen?

Helen's attitude and conflicting treatment of Gilbert make him feel numerous emotions.

To tell you all the questionings and conjectures—the fears, and hopes, and wild emotions that jostled and chased each other through my mind as I descended the hill, would almost fill a volume in itself. But before I was half-way down, a sentiment of strong sympathy for her I had left behind me had displaced all other feelings, and seemed imperatively to draw me back: I began to think, “Why am I hurrying so fast in this direction? Can I find comfort or consolation—peace, certainty, contentment, all—or anything that I want at home? and can I leave all perturbation, sorrow, and anxiety behind me there?”