I just can't seem to accurately judge the spot I am aiming for.
I'm new to this site so not sure if I've extracted the quote correctly.
Anyway in the event of any emergency requiring an auto/PFL you should not be judging the spot you are aiming for (Aircraft flying you) but picking a suitable spot for the forced landing and you flying to it. If this point is static in you windscreen then you will make the spot but if it is moving up or down the windscreen then you are overshooting or undershooting and need to use one of the techniques to make good.
Another common fault is don't select a spot but use a line preferably about 1/3 of the way into a field and use the full width of the field to make that 1/3 line.