I think you're keeping it too dry. Yes they are succulents types of plant but when in active growth they will take a good deal of water, particularly if kept indoors.
I water mine roughly once a week in Summer. You need to water thoroughly, until the water flows out of the drainage holes, you can discard any water after 10 minutes that the plant doesn't take up. Then wait until the top couple of inches of compost feels dry before you water again. The leaf curling is a sure sign of dryness.