As I said before, this plant is an annual, dying at the first hint of frost outside. You could try keeping it as a houseplant as the weather gets colder, when it'll need cool but not cold conditions, away from heat sources and direct sunlight, with regular watering, allowing the surface of the compost to be slightly dry before watering again. Once it finishes flowering, bin it, even as a houseplant, it's only a temporary visitor even in the house.