Erection quality has to do with many things. First, weak pelvic floor muscles can cause weak erections, practicing lots of Kegels and assisted Kegels will help build the strength of these muscles and allow for much stronger erection. Overstimulation, as indicated above, is also a culprit of poor erection quality when abused. Too much of anything will end up being a deficit. Depression and other emotional factors can also point towards poor eq, searching deep in yourself for what is truly bothering you and attacking it with tenacity to correct it will serve you with better erections. Sometimes anxiety can cause poor eq too, this agains is something you will need to approach with cognitive methods. Another reason EQ can be low is fatigue, tiredness or any kind of exhaustion. This happens when we overtrain, ejaculate too much or purposely cause it through DLD Blasters or the Like.