Naa man, you aint the only one. its all about stayin focused...
but yeah, when i started, i felt the same way, lookin at that empty screen is daunting, i now just sit down, import a decent break as a starting point, try t make a quick reese patch, bounce that, then sample it, lay a quick "simple" bassline down, and then repeat the process for a melody and sub, once i have all aspects of the tune, ill then spend time trying to fit it into a decent tune, sometimes it works sometimes it doesnt... if it does then i add more to it and just keep working and if it doesnt, scrap it and start again. I find though if you take too long with each part of the mix, it kills the vibe of the session and you get nowhere. just have to keep at it!