I actually had a similar conversation today with my commercial student.

The most important thing is consistency. A consistent pattern means that the picture as you turn onto final will be the same every time. This allows for a consistent glide path, consistent round out, consistent flare, you get the idea. Of course, none of this will be consistent unless particular attention is paid to airspeed, altitude, configuration, etc. For this, I always give my students "base line" numbers to start with that will allow them to worry less (but still keep an eye on them) about looking at the instruments, and more about looking outside at the RUNWAY (not straight ahead! A big pet peeve of mine). You should be looking at three places: the runway, other traffic ahead of you, and the instruments. Not the cars on the road or off into space. Once the students are familiar with the aircraft and the pattern, they are free to adjust or change those "base line" numbers as they please. With traffic in the pattern or entering from a base/final, just adjust the pattern as needed to make it as normal as possible. The flare and touchdown are different though.

I tell my students to feel the airplane and start developing their sense of how if acts close to the ground. This takes practice, lots of it. I've noticed that most students will struggle for a while but then the "light switch" turns on and they have it down. From an instructor's stand point, we have to remember that the amount of information that a pilot takes in (especially a student pilot) at one time is huge. It can take student's a little while to learn how to process all the information that is given to them and understand/react to it.

Hopefully this helps a little. Keep working on those landings and challenge yourself to make them consistent each and every time. Passengers always judge a pilot on his landing, so always try to make each landing better then the last!