Two friends strolling; a simple concept for a drawing, correct?
The way you set the mood in this wonderful drawing is what sets it apart from anything I've seen before. The colors in the ponies are very pretty, not too saturated and overwhelming. You also shaded their bodies, which adds a small yet impacting detail here.
The poses are very fluid, and combined with the color blur around them, it creates a sense of motion here. Ant the small pebbles at the lower ponies hooves makes it seem as they are running, not for a serious competition, but for a fun run both in the sky and the ground. Their faces are priceless, they look so happy!
Last but not least is the small bird you added, which made a pleasing effect on the picture, as it is part of the lower pony's cutie mark.
Beautiful work overall, simple, yet charmingly upbeat. I hope to see more great drawing from you in the near future.