I agree with the previous post about the airy synth. But I have bigger issues.
Composition-wise, I find the melody to kind of aimless, not memorable or interesting enough, kind of just noodling around. As I'm listening, I'm finding that one note in the melody is as good a choice as any other, there needs to be more "inevitability", if that term makes any sense. When you get to the key change at about 3:00, that's a good idea to perk my interest, and you sort of built to it, but I would take that moment further.
Mix-wise, I would take at least half the reverb off the drums and bass, and reduce it everywhere else as well. I think you'll find it has a lot more energy with much drier drums (though the transition as you turn the fader is initially shocking and sounds scary!). Also, There is a lot of sonic clutter in the low-mid range, I would take some low-end off the pad synth, and removing reverb from bass and drums will help clean that up.
But most importantly, I would spend time pulling the ropes a lot tighter on the tune. Good luck! Ain't all this fun?