It's generally fine to leave Christmas tree lights on, but it's always a good idea to be safe. Make sure to turn the lights off when you leave the house or before you go to bed, and avoid placing the tree near any open flames or heat sources. Additionally, be sure to inspect the lights regularly for frayed wires or other signs of wear and tear that could cause a safety hazard. With proper care, your Christmas tree lights can bring joy and beauty to your home for many years to come.