I've grown sage very successfully by allowing the soil to dry between waterings. since it is winter and the plant is growing slower (and the wilting leaves sound like some early stage root rot) I'd keep it on the dry side. it doesn't need as much water now because in winter plants don't grow as fast. in addition, you likely lost some feeder roots (causing the wilting) so the plant couldn't take up all the water anyway. don't let it dry out completely, but I do wait until soil is dry to touch to water Mediterranean plants (such as sage). if you are really concerned prop a plastic bag over the plant to create a mini greenhouse. use sticks to hold the plastic so it doesn't touch the plant. this will help keep the humidity in until the roots grow back. I've found sage to be very tough, bouncing back after the apocalyptic hellstorms the past few winters in New York have been, and bouncing back after the neighbor's kid mowed down my herb garden. and no, sand is usually added to help soil drain, not to hold water. I use plenty of perlite in mixes for herbs like sage- lots of air and excellent drainage. hope this helps :)

I don't like to use sand in containers...it can act like a compacting ingredient, filling in all of those beneficial nooks and pore spaces with tiny, solid particles. Perlite is always a good addition.....it adds to the essential porosity, it holds oxygen and water (and dissolved elements) throughout the whole container volume, which makes for happy roots.

I've read that you shouldn't use different layers of different soils in the same pot/location; there is some sort of ionic thing that keeps the water contained in the original layer with the next layer acting as a barrier.

Kate, you are correct that the layering of different components can cause problems. It is (almost) always important to combine everything into a homogeneous mixture before using any mixture as a potting medium.

It's important to remember that layering can cause problems with outdoor soils, too, whether occuring naturally or by our hands.