Pick a point on the runway (usually the 300m / 1000ft markers - or if there are none visualise where they would be) and keep that point steady in your windscreen. If it moves down the windscreen you are too high, if it moves up the windscreen you are too low! If it's steady, I promise you that you will land in the TDZ. The PPL manuals say this, as does the FCTM for the 737. Fly approaches like this from now and you are set for life because the way you should fly a visual approach is the same for every aeroplane.
As for the Go-Around situation. If what is happening doesn't appear to be right, it generally isn't right. No thought should be put in to the matter, go around and try again. Accidents happen when people push on, tunnel vision sets in as they focus on landing the aircraft at all costs. No one should ever critisize you for a go-around. All you did was bugger up the approach, but you never buggered up anything else or anyone else by going around!
Goodluck