When you leave a liquid like water on leaves while the succulent is exposed to bright sunlight, there's a chance that the water will act like a magnifying glass and burn the leaf. Make sure you get the whole leaf when using leaves. The rest of the pot should be taken with you. Fungus gnats like moist soil with lots of decaying leaves and plant matter, so if you keep your plant's pot clean and dry, they're less likely to make it their next home. Soil plays a major role. And that part is important - you want to ensure that all of the soil is completely wetted.