I think peoples largest problem (well at least my own) with composition is just sitting there and looping something until it sounds JUST right. And then when it actually is just right you don't even know it because you're bored with the sound and end up scrapping it. I used to do this all the time. Experimenting and tweaking is great but a lot of music is flow. I usually find a way to clear my mind of all the junk going around inside of it before I seriously sit down to write a song. Meditate, go for a walk, smoke (heh, not to sound typical but it generally gets my workflow moving pretty fast, things sound great and I keep moving

Spend your time more in the arrange view than in the session view. Try writing simple things, then arranging, create a chorus verse etc, then working your way down. Try to get a two or three minutes of a song before you start doing technical editing, just get it done first. You've gotta move fast enough at the start before you get bored with it.
These are just some things that took me a long time to realize, and to make habits out of. Realizing that most of my workflow problems of never getting songs done wasn't the programs fault and that it was mostly me being impatient. I probably went back and force from like 20 different sequencing programs and techniques and then just kept searching for something that fit "me", and then finally realized that my view on writing music itself was what was really slowing me down.
Sorry for the rant but I think these things are really important and something most people don't want to admit to themselves because its actual hard work. In fact, so much about life I learned from writing music

Or maybe I'm just wierd.
