The problem is usually that you are looking at the point on the runway at which the glider is aiming. The trick is to switch your attention to the far end of the runway (or at least half way along it) at around 50ft, and start very gently easing back on the stick about then. If you're looking at the runway in front of the nose you can't judge height, and suddenly the ground rushes you. If you're looking into the distance you can see the aircraft settling and ease back on the stick as needed.
As prof. Reed says, looking a long way ahead is the key - once you are over the landing area, switch your focus to the far end of the field.
Another thing that helps your landings is to actually change your thinking and try NOT to land! It sounds silly, but you should actually be aiming to keep flying as long as possible - "aim at the ground and miss for as long as possible"! Keep the wings level and tracking straight, just let the glider settle gently - it will land itself, provided you keep it flying!
Forcing it down will just end up in hard landings, bounces and balloons.
So for good landings, try not to land!
FBW