Okay, I listened, and have a few suggestions. Note that I am not a music recording engineer or anything like that. This is just based on what I heard and how I think it could be improved.
It sounds incomplete, mainly because it's not mastered? I realize Garageband has limitations, but a lot of the volume issues can be addressed manually by monitoring closely, and adjusting the various tracks so they blend nicely, and don't overpower each other to the point of distraction. I noticed the percussion varied greatly. When you were hitting cymbals, the volume was good, but when you hit the snare it was startling. This made the entire song seem out of rhythm.
The piano is what remained constant enough to maintain any semblance of rhythm in this song, and had decent volume. The vocals were okay, you have a nice voice. I would try to put more feeling into them, though. At times you sounded like you just woke up, and at other times, you sounded more like you were into your performance. Did you put an effect filter on the vocal track? It sounded a bit like you were singing in a vacuum?
My suggestion on the vocals is to sing it again when you're feeling rather passionate about the fact that you composed your own song from scratch. That's quite a feat, and it took a lot of courage to post it publicly. After you've recorded the vocals again, copy and paste the vocal track into the mix again. With double tracks for vocals, it will help strengthen your voice and improve the sound.
I would also record the percussion track again, and instead of hitting the snare full on, I would do rim shots? Then adjust the volume of that track so it's more consistent and softer. This is a love song, so it should be soft and warm. You did a good job enunciating the lyrics. I could understand them easily.
Don't apply any filters on any tracks at all until you're mastering. Then make sure the filters you use don't detract from the song, but merely tweak it a bit? You can adjust filters in Garageband pretty easily. I'll assume you know how, but if not, let me know and I'll do my best to assist. Also, when you are mastering, try monitoring it through speakers as well as headphones, and tweak so that it sounds decent in both.
Congrats on composing/performing/recording your song. I can't wait to hear it again after you've had time to work on it a bit more.
