The human mind can only focus on a maximum of 4 things at any one time. You're doing something wrong if you aren't focusing on the target (that's one thing). Add in your draw, travel (hopefully towards cover or at least towards concealment), grip mechanics, trigger control, sight picture and you are already overwhelmed.
Sometimes it's best to just shoot. Don't think, just act. This assumes you are practicing on a regular basis of course- the fundamentals are the basis for any skill. If you're learning focus on one or two fundamentals at a time and build on that until it becomes instinctive.
Some good advice on building incremental continuity is here (thanks to Indestructible Training).