Hi!!!! You're not doing anything wrong at all, just feeling out what it means to be an editor. I think what you're feeling is a mismatch of pace. Probably the hardest thing for me to do on my first amv was to speed it up. It felt like it was going way too fast but watching it back later it could have gone faster. Don't go crazy or anything though.
Try listening to the song and close your eyes, feel the most natural beat and get it ingrained in your head. Then go back and put a clip beginning on each of those beats. This is a good song to try that out on since it has such a nice natural beat that's not too complicated. Of course you don't have to keep those beats the same in your final copy but it should help you to get a better pace started.
Just try your hand at it, so far it looks like you have a vision and it's just the getting it out there that's difficult. But be encouraged! It's the same for us all.
