For me, what works best is the background. It's blended real smoothly and gives off the warm feel. It also doesn't distract from the main subject. Though I must say that the reflection of the Sun extends too far out on the right. Try cropping it so that it's symmetrical on each side. As for the pony, I do admire how you placed the sparkles all throughout the aura to enhance the magical feel. Yet I find it confusing as to why she needs to carry herself across the lake since she has wings. Furthermore, I would try to make sure the front and back legs are evenly sized, and the cutie mark could be just a little
smaller. Of course, this isn't a bad drawing. Some of the techincal aspects such as the well-blended background and shine in her mane are pleasing to look at. I'm just compelled to question certain things that don't add up, and the execution could use some improvement. Still, I advise you to keep up the awesome work, SunriseSparkle!