The candle grows shorter while making the room larger to the eye.

Something is consumed in order to give. The candle can only make the room visible by using itself up, and the light and the shortening are the same process rather than two separate events. A great deal of giving works like this and is not thereby a tragedy.

What matters is whether you are spending yourself on something you would choose. Rather than trying to give without cost, which is not available, ask whether the room you are lighting is one you want lit. And accept that some of your energy is meant to be spent, which is different from being taken.