Pardon my rant in advance. Each and every new melodic line/instrument that you introduce gets louder and louder and towards the end drowns out everything else (and does so unevenly). The reverb doesn't help, as it muddles things up - sometimes that's the desired effect and works well, but not here. The piece sounds fine until the second set of string and brass kick in - that's when it starts to muddle bad. I'd use the mixer a little more - try bringing levels of all the instruments down in there and notch off some of that reverb - it should help clear things up a little. I listened to the original piece to see if it suffers from the same: yes and no. It's got slightly excessive reverb, too, imho, but it works better because the instruments aren't drowning each other out nearly as much. Another way you can help clear it up is by simply reducing the number of instruments still playing in the background as you introduce new ones - then the new ones don't have to be as loud to get through. Don't be afraid of silence, by the way - you should have some silent or quiet moments in a piece to contrast the loud ones. And no worries, I've done the same mistakes before, and learned the hard way. Hope this helps :)