The presence of sloth and torpor does not mean that energy is not available. It means we are not accessing it. With a change in conditions, energy may reappear in a moment. This can be seen clearly in young children who switch from being “tired” (while shopping, for instance) to being energetic (about an offer of ice cream) in a matter of seconds. The energy level depends on whether they evaluate the situation as boring or exciting. The Hindrance of Sloth and Torpor
~ Gil Fronsdal