terok,
In 1982 when I was doing my PPL (just threw that in so you know I am an old git) I had exactly the same problem. My instructor, a great bloke called Don Walker (RIP) told me to look out of the side window to help judge my height and it worked. After a few landings it came naturally and I no longer needed to do that.
A instructor recently told me he teaches 150 students to hold the nose level with the far end of the runway, it makes for functional rather than greased landing, but is consistent.